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Issued  September  20,  1911. 

U.  S.  DEPARTMENT  OF  AGRICULTURE, 

FOREST  SERVICE— BULLETIN  75. 

HENRY  S.  GRAVES,  Forester. 


CALIFORNIA  TANBARK  OAK. 


PART    I.  Tanbark  Oak  and  the  Tanning  Industry. 

By  WILLIS  LINN  JEPSON,  Collaborator. 

t* 
PART  II.  Utilization  of  the  Wood  of  Tanbark  Oak. 

By  H.  S.  BETTS,  Engineer  in  Timber  Testa,    .  ( 

APPENDIX.  Distribution  of  Tannin  in  Tanbark  O»k*. : ' 

By  C.  D.  MELL,  Assistant  Dendrologist;'  *   /    : 


SEC 


OCT  29  1914 

Division  of  Forestry 
University  of  California 


WASHINGTON: 

GOVERNMENT  PRINTING  OFFICE. 
1911. 


LETTER  OF  TRANSMITTAI, 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

FOREST  SERVICE, 

'•./  :  I/: :  :  Washington,  D.  C.,  March  13,  1911. 

*SiR:  1  have.,  the  honor  to  transmit  herewith  a  manuscript  entitled 
!?tCaJffiryia.'Ta2jbark  Oak/'  by  Willis  Linn  Jepson,  collaborator,  and 
H.  S.  Betts,  engineer  in  timber  tests,  together  with  an  Appendix  by 
C.  D.  Mell,  assistant  dendrologist,  and  to  recommend  its  publication 
as  Bulletin  75  of  the  Forest  Service.  This  bulletin  shows  how  the 
complete  product  of  tanbark  oak— its  bark  and  its  wood — may  be 
utilized.  It  is  important  that  this  complete  utilization  should  be 
brought  about.  The  wood  is  now  left  in  the  forest  to  rot  unused  or 
to  add  fuel  to  forest  fires.  The  timber  tests  show  that  the  lumber 
has  a  high  value  and  can  be  put  to  the  same  uses  to  which  the  eastern 
oaks  are  put.  A  careful  handling  of  woodlands,  coupled  with  con- 
servative lumbering,  ought  to  make  the  tanbark-oak  crop  continuous 
and  render  this  resource  inexhaustible. 

Respectfully,  .  HENRY  S.  GRAVES, 

Forester, 
Hon.  JAMES  WILSON, 

Secretary  of  Agriculture, 
2 


CONTENTS.     \ 


PART  I. — TANBARK  OAK  AND  THE  TANNING  INDUSTRY. 

Page. 

Development  of  the  tanning  industry  in  California 5 

Silvical  characteristics  of  the  tanbark  oak 6 

Range  and  occurrence 7 

Associates 8 

The  production  of  tanbark 8 

Centers  of  the  industry 8 

Stand  and  yield 9 

Peeling 10 

Transportation 12 

Quality  of  the  bark 14 

Prolonging  the  supply 15 

Providing  for  second  growth 16 

Sprout  reproduction 16 

Reproduction  by  seed 17 

Second-growth  bark 17 

Quality  of  second-growth  bark 18 

Conservative  methods  in  the  woods 19 

Guarding  against  fire 19 

Tannin-extract  processes 20 

Supplemental  materials 21 

Possibilities  of  utilizing  the  wood 22 

Conclusions 23 

PART  II. — UTILIZATION  OF  THE  WOOD  OF  TANBARK  OAK. 

Tanbark  oak  lumber 24 

Appearance  and  characteristics  of  the  wood 24 

Strength '. 25 

Seasoning 28 

Shrinkage 29 

Hardwoods  used  on  the  coast 30 

Suggested  uses  for  tanbark  oak 31 

APPENDIX. 

Distribution  of  tannin  in  tanbark  oak 33 

3 


477598 


: 


LETTER  OF  TRANSMITTAL 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

FOREST  SERVICE, 

\:  •  «/:  *•  •  Washington,  D.  C.,  March  13,  1911. 

"SiR*  1  have.4he  honor  to  transmit  herewith  a  manuscript  entitled 
t^*ta!ifC)riiia."Tai?bark  Oak/'  by  Willis  Linn  Jepson,  collaborator,  and 
TEE  S.  Betts,  engineer  in  timber  tests,  together  with  an  Appendix  by 
C.  D.  Mell,  assistant  dendrologist,  and  to  recommend  its  publication 
as  Bulletin  75  of  the  Forest  Service.  This  bulletin  shows  how  the 
complete  product  of  tanbark  oak — its  bark  and  its  wood — may  be 
utilized.  It  is  important  that  this  complete  utilization  should  be 
brought  about.  The  wood  is  now  left  in  the  forest  to  rot  unused  or 
to  add  fuel  to  forest  fires.  The  timber  tests  show  that  the  lumber 
has  a  high  value  and  can  be  put  to  the  same  uses  to  which  the  eastern 
oaks  are  put.  A  careful  handling  of  woodlands,  coupled  with  con- 
servative lumbering,  ought  to  make  the  tanbark-oak  crop  continuous 
and  render  this  resource  inexhaustible. 

Respectfully,  .  HENRY  S.  GRAVES, 

Forester. 
Hon.  JAMES  WILSON, 

Secretary  of  Agriculture, 
2 


CONTENTS.     \ 


PART  I. — TANBARK  OAK  AND  THE  TANNING  INDUSTRY. 

Page. 

Development  of  the  tanning  industry  in  California 5 

Silvical  characteristics  of  the  tanbark  oak 6 

Range  and  occurrence 7 

Associates 8 

The  production  of  tanbark 8 

Centers  of  the  industry 8 

Stand  and  yield 9 

Peeling 10 

Transportation 12 

Quality  of  the  bark 14 

Prolonging  the  supply 15 

Providing  for  second  growth 16 

Sprout  reproduction 16 

Reproduction  by  seed 17 

Second-growth  bark 17 

Quality  of  second-growth  bark 18 

Conservative  methods  in  the  wroods 19 

Guarding  against  fire 19 

Tannin-extract  processes 20 

Supplemental  materials 21 

Possibilities  of  utilizing  the  wood 22 

Conclusions 23 

PART  II. — UTILIZATION  OF  THE  WOOD  OF  TANBARK  OAK. 

Tanbark  oak  lumber 24 

Appearance  ajid  characteristics  of  the  wood 24 

Strength '. 25 

Seasoning 28 

Shrinkage 29 

Hardwoods  used  on  the  coast 30 

Suggested  uses  for  tanbark  oak 31 

APPENDIX. 

Distribution  of  tannin  in  tanbark  oak 33 

3 


477598 


ILLUSTRATIONS. 


PLATES. 

Page. 

PLATE  I.  What  is  left  after  the  tanbark  is  removed Frontispiece. 

II.  Typical  tanbark  oak  country  where,  in  the  redwood  belt,  the  tree 

attains  its  best  development 8 

III.  Fig.  1. — Typical  tanbark  oak  tree  undergoing  removal  of  first  ring  of 

bark.     Fig.  2. — Closer  view  of  the  operation 12 

IV.  Fig.  1.— Peeling  4-foot  rings  of  bark  from  the  felled  tree.     Fig.  2.— 

Bunching  the  bark  in  small  piles  along  the  sled  road 12 

V.  Fig.  1. — The  skid  ways  to  which  the  bunched  bark  is  sledded,  and 
from  which  it  is  hauled  to  the  railroad.     Fig.  2. — Hauling  the  bark 

in  wagons  from  the  skidways  to  the  cars 12 

VI.  Fig.  1. — Machine  and  method  used  for  testing  small  beams.    Fig.  2. — 
Seasoning  checks  in  the  butt  of  a  tanbark  oak  log  exposed  to  the  hot 

sun  for  six  weeks 24 

VII.  Fig.  1. — Tanbark  oak  lumber  for  car  construction.     Fig.  2. — Tan- 
bark  oak  boards  air-drying 24 

VIII.  Fig.  1. — Tanbark  oak  flooring,  and  the  method  of  storing  and  sorting  it. 

Fig.  2. — Tanbark  oak  flooring  ready  for  shipment  from  the  mill. .         28 
IX.  Transverse  section  of  a  2-year-old  twig  of  tanbark  oak,  showing  tannin 

in  the  pith,  pith-rays,  and  bark 28 

X.  Fig.  1. — Transverse  section  of  a  3-year-old  twig  of  tanbark  oak,  show- 
ing the  distribution  of  tannin  in  the  pith  and  pith -rays.     Fig.  2. — 

Longitudinal  radial  section  of  a  3-year-old  twig 28 

4 


uu 


OCT  29  1914 

Division  of  Forestry 
University  of  California 


CALIFORNIA  TAN  BARK  OAK. 


a) 

PART  I.— TANBARK  OAK  AND  THE  TANNING  INDUSTRY,1 

By  WILLIS  LINN  JEPSON. 
DEVELOPMENT   OF  THE   TANNING  INDUSTRY   IN  CALIFORNIA. 

Tanbark  oak  is,  economically,  the  most  important  of  the  15  Pacific 
coast  oaks,  because  it  furnishes  the  chief  material  used  in  the  exten- 
sive tanning  industry  of  that  region.  In  1900,  according  to  the 
census,  California  ranked  third  among  the  States  in  the  value  of 
tanned  hides  produced.  Commercial  tanning  on  the  Pacific  coast 
began  with  the  influx  of  Americans  into  California  in  1849  and  1850. 
As  early  as  1852  Sonoma  County  had  one  tannery  which  produced 
$30,000  worth  of  leather,  and  by  1856  there  were  18  in  the  State,  in 
which  $94,000  was  invested.  The  bark  of  the  tanbark  oak  was  first 
used  at  Santa  Cruz,  and  in  1857  a  tannery  there  with  an  output  of 
700  hides  a  month  was  the  largest  in  the  State.  Its  leather  was 
superior  to  that  produced  by  the  establishments  which  still  used  the 
live-oak  and  black-oak  bark,  the  first  utilized.  By  1859  there  were 
29  tanneries  and  their  product  was  more  than  sufficient  for  home 
consumption.  In  the  next  year  the  value  of  the  output  of  the  State's 
tanneries  was  $276,014,  and  seven  years  later,  in  1867,  there  were 
more  than  40  establishments,  with  an  annual  product  worth  $400,000. 

The  development  of  the  tanbark  industry  since  1850  is  shown  by 
Table  1. 

TABLE  I.— Tan  oak  bark  harvested  in  California,  1855  to  1907. 


Annual  product. 

Annual  product. 

Product  by  periods. 

Year. 

Cords. 

Y«ar. 

Cords. 

Years. 

Cords. 

1855 

1,000 
3,000 
8,000 
15,000 
21,000 
24,000 
24,000 

1893 

20,000 
20,000 
25,000 
30,000 
25,000 
30,000 
20,000 

1851-1860 

15,000 
.55,000 
147,500 
240,000 
218,500 
185,000 
861,000 

1860  

1895  

1861-1870 

1870..    . 

1900 

1871-1880 

1875 

1904 

1881  1890 

1880  

1905 

1891-1900 

1881 

1906 

1901-1907  (7  years)  
1851-1907  

1890  

1907 

i  In  gathering  the  data  upon  which  this  report  is  based  the  author  received  assistance  and  helpful  courte- 
sies from  many  people  directly  or  indirectly  connected  with  the  tanbark  industry  on  the  Pacific  coast. 
Their  number  was  too  great  to  permit  of  individual  acknowledgment  here,  but  the  author  takes  this  means 
to  thank  them  for  the  great  assistance  given  him. 

5 


CALIFORNIA    TAXBARK    OAK. 


At  $18  per  cord,  an  average  of  the  prices  since  1850,  the  value  of 
the  bark  produced  in  the  period  1851-1907  would  be  $15,498,000. 
Practically  all  of  this  has  been  consumed  in  the  manufacture  of  heavy 
leather  used  for  belting,  harness,  saddles,  and  soles.  The  California 
tanneries,  up  to  1907,  turned  out  250,000,000  pounds  of  such  leather, 
valued  at  $75,000,000. 

SILVICAL   CHARACTERISTICS   OF  THE   TANBARK  OAK. 

Tanbark  oak  (Quercus  densiflora  H.  &  A.)  grows  to  be  from  50  to 
140  feet  high  and  from  1  to  6  feet  in  diameter.  There  are  four  general 
forms  of  growth — the  roundheaded;  the  spire-shaped,  similar  to  coni- 
ferous trees;  the  shrubby,  deep-shade  form;  and  the  stunted  cha- 
parral form.  In  open  situations,  or  in  association  with  madrona  and 
California  black  oak,  the  main  trunk  subdivides  into  a  number  of 
large  branches  and  forms  a  rounded  head,  although  the  height  of  the 
crown  is  greater  than  its  width.  In  dense,  coniferous  forests  it 
assumes  the  spire  or  cone  shape  of  the  trees  with  which  it  is  associated, 
and  these  trees  are  tallest  and  have  the  straightest  trunks,  with  a 
clear  length  of  from  30  to  80  feet.  Under  stands  of  mature  Douglas 
fir  or  redwood  there  may  be  abundant  low,  shrubby  growths  of  tan- 
bark  oak,  since  the  tree  is  remarkably  shade  enduring,  and  when  the 
dominant  forest  cover  is  removed  the  tanbark  oak  promptly  takes 
possession  of  the  logged  areas.  This  is  exemplified  especially  on  the 
Mendocino  coast.  In  the  interior  of  California,  around  Mount  Shasta, 
the  stunted  tanbark  oak  in  the  midst  of  chaparral  assumes  many  of 
the  characteristics  of  the  shrubs  by  which  it  is  surrounded,  such  as 
low  stature,  rigid  branches,  and  small,  thin  leaves.  This  chaparral 
form  (var.  ecJiinoides)  is  worthless  for  tanbark. 

Tanbark  oak  has  many  chestnutlike  characteristics.  In  the 
character  of  its  male  flowers  the  tree  is  a  chestnut,  but  in  the  character 
of  its  female  flowers  and  in  its  habit  it  is  an  oak.  By  some  authors 
it  is  referred  to  the  genus  Pasania,  which  includes  nearly  1 00  species 
in  southwestern  Asia. 

The  oaklike  characters  and  the  chestnutlike  characters  are  com- 
pared in  the  following  tabulation: 


CHESTNUTLIKE   CHARACTERS. 

Parallel  nerves  of  the  toothed  leaves. 

Erect  catkins. 

Pistillate  flowers  in  same  catkins  as 
staminate. 

Stamens  of  male  flowers  very  much  ex- 
ceeding calyx;  rudiments  of  stamens  in 
pistillate  flower. 

A. corns  with  suggestion  of  burriness.  Nut 
often  vaguely  triangular. 


OAKLIKE    CHARACTERS. 

Bark  very  like  typical  oak  bark. 
Involucre  1-flowered. 
Ovary  3-celled. 


Cup  of  the  acorn  a  true  cup  and  not  a 
closed  involucre.  Kernel  oaklike,  bit- 
ter to  the  taste. 


SILVICAL    CHARACTERISTICS.  7 

The  chestnutlike  leaves  are  from  2  to  5  inches  long  and  are  borne 
on  short  petioles.  The  teeth  are  small  and  scattered.  Sometimes 
the  margin  is  entire  near  the  base  or  even  for  its  whole  extent, 
especially  on  narrow-leaved  forms.  This  variation  in  leaf  form 
sometimes  leads  woodsmen  to  speak  of  "two  kinds  of  tanbark  oak." 
Both  surfaces  of  the  leaf,  especially  the  lower,  are  covered  with  a 
thick,  light-colored,  dusty  fuzz,  which  gives  the  foliage  a  distinctive 
hue. 

The  flowers,  which  appear  in  July  or  August,  often  conceal  the 
foliage  with  a  mass  of  grayish-white  blossoms.  The  acorns  are 
from  f  inch  to  1J  inches  long,  and  from  f  to  1  inch  broad,  and  coated 
with  a  brown  fuzz.  The  somewhat  burrlike  but  shallow  cup  is 
covered  with  long  and  narrow  scales. 

The  bark  of  the  trunk  of  adult  trees  is  usually  from  1  to  3  inches 
thick,  and  sometimes  from  4  to  5  inches;  it  is  brown,  smooth  on 
the  surface,  but  so  fissured  longitudinally  and  transversely  as  to 
produce  elongated,  irregularly  rectangular  plates.  On  the  main 
limbs  and  on  young  trunks  the  bark  is  very  smooth,  little  fissured, 
if  at  all,  white,  gray,  or  mottled,  and  often  strikingly  similar  to  the 
bark  of  red  alder. 

RANGE    AND    OCCURRENCE. 

The  range  of  tanbark  oak  extends  from  a  little  north  of  the 
Umpqua  River  in  southwestern  Oregon  through  the  coast  ranges  to 
Santa  Barbara  in  California,  and  from  the  Humboldt  region  eastward 
by  way  of  the  Shasta  Mountains  to  the  Sierra  Nevada,  and  along 
that  range  as  far  south  as  El  Dorado  County. 

In  general,  though  not  always,  tanbark  oak  grows  either  with 
redwood  or  in  the  neighborhood  of  the  redwood  belt.  It  is  an 
associate  of  redwood  in  all  the  great  redwood  areas  and  even  in  the 
isolated  bodies  or  tongues  in  the  range  of  that  tree.  The  greatest 
forests  of  redwood  are  in  Mendocino  and  Humboldt  Counties,  and 
in  those  counties  tanbark  oak  attains  its  best  development.  (PL  II.) 
Tanbark  oak  is  not  at  its  best,  however,  in  the  heart  of  the  redwood 
forests,  but  in  the  belts  which  border  them.  The  principal  body  of 
tanbark  oak  forms  a  band  along  the  inland  side  of  the  redwood  belt 
and  covers  the  "Bald  Hills."  The  general  term  "Bald  Hills" 
is  a  widely  used  folk  name  for  the  inland  portion  of  the  seaward  Coast 
Range,  that  much-broken  mountain  range  which  parallels  the  coast 
and  separates  the  ocean  from  such  valleys  as  those  of  Santa  Rosa, 
Alexander,  and  Ukiah^nd  the  narrow  canyon  of  the  main  Eel  River 
in  its  long  course  from  Little  Lake  Valley  northward  to  Humboldt. 

The  higher  inner  ridges  and  summits  and  the  interior  slopes  are 
covered  by  a  mixed  forest  forming  the  tanbark  oak  belt  along  the 
whole  length  of  the  main  redwood  body.  In  southern  Humboldt, 


8  CALIFORNIA   TANBARK   OAK. 

however,  the  tanbark  oak  belt  pushes  through  the  great  transverse 
break  in  the  redwood  belt  at  that  point,  and  an  arm  extends  north- 
ward over  the  Wilder  Ridge  country  to  the  Rainbow  Range.  This 
extensive  and  excellent  virgin  body  borders  the  redwood  belt  on  the 
outside  and  covers  a  considerable  portion  of  the  Mattole  country 
lying  between  the  redwood  belt  and  the  ocean. 

In  the  region  around  Eureka  the  redwood  stand  is  so  exceedingly 
dense  that  it  practically  occupies  the  whole  country  to  the  exclusion 
of  tanbark  oak.  In  the  redwood  forests  along  the  main  Eel  River, 
on  the  Mad  River,  and  on  Smith  River  tanbark  oak  grows  not  at  all 
or  merely  as  tare  individuals.  Here  it  is  necessary  to  pass  through 
the  redwood  belt,  or,  what  is  usually  the  same  thing,  to  gain  the 
summits  of  the  ridges  at  the  headwaters  of  the  coast  streams,  to 
find  tanbark  oak.  To  the  south  this  is  not  the  case.  In  Mendocino 
County  tanbark  oak  occurs  throughout  the  redwood  belt.  There, 
however,  tanbark  oak  trees  in  the  main  redwood  stands  areisually 
small  and  scattering,  and  it  is  only  on  the  summits  above  the  redwood, 
and  particularly  on  the  inner  summits  and  ridges,  that  the  trees  are 
abundant  and  of  large  size. 

ASSOCIATES. 

Tanbark  oak  never  forms  a  pure  stand.  The  tanbark  oak  belt 
consists  of  a  mixed  forest  of  broadleaf  and  coniferous  trees.  Its 
most  common  associates  besides  redwood  are  Douglas  fir,  which, 
except  in  Santa  Barbara  County,  occurs  with  it  throughout  its 
range;  madrofia  (Arbutus  menziesii),  its  most  common  associate, 
which  reaches  very  large  dimensions  in  the  tanbark  oak  belt;  Oregon 
post  oak  (Quercus  garryana),  the  most  abundant  of  the  true  oaks  in  the 
whole  tanbark  oak  belt;  California  black  oak  (Quercus  calif ornica) , 
on  all  the  higher  ridges,  or  high,  fertile  hill  slopes;  and  western 
chinquapin  (Castanopsis  chrysophylla) ,  an  associate  in  the  regions  of 
its  best  development. 

THE   PRODUCTION  OF  TANBABK. 
CENTERS    OF   THE    INDUSTRY. 

The  Santa  Cruz  district  has  been,  from  the  first,  one  of  the  most 
important  sources  of  tanbark,  because  the  tanneries  at  Santa  Cruz, 
San  Jose,  Santa  Clara,  and  Redwood  City  could  be  supplied  by 
wagons  direct  from  the  woods,  and  this  obviated  long  and  costly 
shipment  by  rail  or  water.  Seventy-five  per  cent  of  the  original 
stand  has  been  peeled,  but  recently  second-growth  trees  have  begun 
to  furnish  a  bark  which  is  acceptable  to  tanners.  Sonoma  County 
has  been  an  important  source  for  30  or  40  years,  and  its  status 
now  is  about  the  same  as  that  of  the  Santa  Cruz  district.  For  the 


Bui.  75,  Forest  Service,  U.  S.  Dept.  of  Agriculture. 


PLATE  II. 


OCT29I9I4 

of  Forestry 


PRODUCTION    OF   TANBARK.  9 

last  17  years  the  chief  source  has  been  the  Mendocino  district,  along 
the  coast  to  the  north  of  Sonoma,  where  tanbark  has  been  outranked 
only  by  redwood  as  a  valuable  forest  product.  This  region  has 
furnished  probably  more  bark  than  all  others  put  together,  but  45 
per  cent  of  the  stand  has  been  peeled  now  and  a  considerable  portion 
of  the  remainder  is,  under  present  conditions,  too  inaccessible  to  be 
of  value.  The  stand  in  the  Santa  Lucia  Mountain  region,  along  the 
coast  in  Monterey  County,  which,  though  of  excellent  quality,  was 
never  large,  is  now  almost  exhausted.  In  the  isolated  Santa  Bar- 
bara district  and  in  the  Sierra  Nevada  territory  the  trees  are  few  and 
scattered. 

The  most  extensive  bodies  of  virgin  tanbark  oak  now  are  in  the 
north — in  northern  Mendocino  and  Humboldt  Counties — and  because 
of  accessibility  to  shipping  the  main  sources  of  supply  are  in  the  coast 
region  of  Mendocino,  southern  Humboldt,  and,  to  some  extent, 
Sonoma  Counties  in  California,  and  in  southwestern  Oregon.  The 
Sonoma  and  Mendocino  areas  have  been  drawn  upon  from  the  inte- 
rior, also,  by  a  railroad  which  follows  the  valleys  of  Santa  Rosa, 
Russian  River,  and  Little  Lake  northward,  and  has  now  reached 
the  center  of  Mendocino  County.  The  most  northern  part  of  the  belt 
has  not  been  much  disturbed,  since  the  railroad  has  not  reached  it 
and  its  distance  from  the  ocean  necessitates  a  long  haul.  The  tan- 
neries at  Humboldt  Bay  have  been  supplied  from  Kneeland  Prairie 
and  the  Acorn  region  in  the  Bald  Hills  country. 

STAND    AND    YIELD. 

It  is  estimated  that  'there  are  now  1,425,000  cords  of  standing  bark 
in  the  Pacific  coast  forests,  distributed  as  follows: 


Counties. 


Cords. 


California: 


San  Mateo,  Santa  Cruz,  and  Monterey 

Marin,  Sonoma,  and  Napa 

Mendocino . : 

Humboldt,  Trinity,  western  Siskiyou,  and  Del  Norte 


Oregon: 


100,000 

70,000 

320,000 

87,5,000 


Curry  and  Coos. 


60,000 


Total.. 


1,425,000 


At  the  present  rate  of  consumption,  this  is  enough  to  provide  for 
the  needs  of  the  leather  industry  in  California  for  a  little  less  than 
half  a  century. 

The  average  yield  of  bark  is  from  200  to  350  cords  per  "claim," 
or  quarter  section  (from  1J  to  2^  cords  per  acre).  From  350  to  640 
cords  (from  2J  to  4  cords  per  acre)  is  considered  a  particularly  good 
yield,  and  exceptionally  fine  quarter  sections  yield  from  640  to  1,200 
cords  (from  4  to  7J  cords  per  acre).  The  highest  yields  are  not 
89446°— Bull  75—11 2 


10 


CALIFORNIA   TANBARK    OAK. 


uncommon  in  the  best  parts  of  the  southern  Humboldt  and  northern 
Mendocino  district,  where  the  stand  in  limited  areas  is  nearly  pure 
tanbark  oak.  The  largest  amount  of  bark  ever  reported  from*  one 
"claim"  was  1;284  cords,  or  8  cords  per  acre. 

In  estimating  tanbark  in  the  Santa  Cruz,  Mendocino^and  southern 
Humboldt  districts  cruisers  generally  count  6  tree^to  the.  cord, 
though  sometimes  the  trees  are  so  large  that  it  takes  'only  4*ito  pro- 
duce a  cord.  In  the  northern  Humboldt'  district  8  or  9  trees /make 
a  cord  and  hi  the  Klamath  14.  Cruisers  are  more  likely  to  under- 
estimate than  to  overestimate  a  claim.  Exceptionally  large  trees 
with  thick  bark  produce  from  2  to  3J  cords  of**bark.  The  figures 
given  in  Table  2  are  from  trees  on  the  inner  edge  of' the  redwood  belt. 

TABLE  2. — Amount  of  tanbark  on  oak  trees  of  different  sizes. 


Diameter, 

Height. 

Length  of 
peeled 
trunk. 

Diameter 
of  peeled 
trunk  at 
upper  end. 

Age. 

Weight  of  bark. 

Dry  weight  of 
bark  (calcu- 
lated). 

Inches. 

Feet. 

Feet. 

Inches. 

Years. 

Pounds. 

Pounds. 

4-  9 

30-  50 

4-  8 

3-  6 

20-  40 

15-      80 

10-      70 

10-12 

40-  80 

16-32 

5-  8 

40-100 

80-    350 

70-    250 

13-18 

80-100 

32-65 

7-12 

70-125 

350-    900 

250-    650 

19-24 

90-120 

65-80 

7-11 

100-159 

900-1,700 

650-1,200 

24-36 

115-140 

80-95 

9-11 

125-180 

1,700-2,500 

1,200-1,800 

36-48 

100-120 

80-90 

9-18 

350-210 

2,  500-4,  000 

1,800-2,800 

48-60 

100-120 

80-90 

9-18 

170-250 

3,  500-8,  000 

2,  500-5,  700 

To  avoid  discrepancies  due  to  loose  piling,  the  "cord"  used  in 
selling  tanbark  is  reckoned  by  weight  rather  than  by  dimension,  and 
is  approximately  a  ton,  though  it  varies  in  different  localities  from 
2,200  to  2,600  pounds.  It  is  most  commonly  2,400  pounds,  which  is 
the  standard  accepted  in  San  Francisco.  For  bark  that  has  been 
peeled  a  year,  2,300  pounds  is  considered  a  ton.  Very  rarely  a  cord 
is  measured  by  dimensions;  but  where  it  is,  as  at  Arcata,  for  instance, 
it  is  8  feet  long,  4  feet  wide,  and  4|  feet  high. 

PEELING. 

The  peeling  season  runs  from  about  May  20  to  about  August  10, 
but  varies  with  latitude,  weather,  and  locality.  Peeling  can  be 
started  any  time  after  the  sap  begins  to  run  and  continues  during  the 
period  of  summer  growth.  Tanbark  oak  is  extremely  sensitive  to 
heat  and  cold  as  regards  the  adhesion  of  its  bark.  A  cold  spring 
-delays  the  opening  of  the  peeling  season  and  a  cool,  moist  summer 
prolongs  it.  Trees  on  the  shady  north  slopes  will  peel  later  than 
those  on  the  ridges  or  south  slopes,  but  one  of  the  periodic  north 
winds  of  the  Coast  Range,  which  are  hot  and  dry,  will  make  peeling 
difficult  or  cause  some  trees  to  bind  down  completely.  Cold  nights, 
on  the  one  hand,  will  make  the  bark  stick,  and  a  hot  period  in  July  or 
August  will  put  an  end  to  peeling.  Trees  standing  side  by  side  often 


PRODUCTION    OF   TANBARK.  11 

show  different  sensitiveness  to  weather  changes;  even  two  sides  of  a 
tree  may  differ  in  ease  of  peeling  and  the  north  side  stick  before  the 
other. 

Peeling  is  also  affected  by  injury  from  fire,  wind,  or  snowstorms. 
Trees  which  are  only  slightly  hurt  by  fire  will  not  peel  for  two  or  three 
seasons,  and  sometimes  not  at  all.  The  wounds  made  when  limbs  are 
broken  off  by  windstorms  or  by  the  weight  of  snow  have  a  similar 
effect.  Even  the  "try  marks"  on  trees  which  are  found  not  ready  to 
peel  interfere  with  satisfactory  work  later  in  the  season. 

Peeling  can  be  done  more  economically  in  the  latter  part  of  the 
season  because  the  bark,  which  is  brittle  in  the  early  part,  becomes 
tougher  then,  so  that  it  can  be  taken  off  in  entire  pieces. 

At  least  half  a  day  is  required  for  two  men  to  peel  a  large  tree.  The 
peelers,  therefore,  never  begin  late  in  the  day  upon  a  tree  which  they 
must  leave  unfinished  until  the  next  morning,  as  the  bark  may  "  bind 
down"  overnight. 

The  peelers  work  in  pairs.  Usually  they  rely  on  the  woodsman's 
one-edged  ax  alone,  as  they  believe  that  the  advantages  of  a  spud 
do  not  equal  the  saving  of  time  when  the  ax  alone  is  used.  With  the 
blade  of  his  ax  the  peeler  tries  the  bark  to  determine  if  it  is  loose, 
and  if  it  is  he  cuts  two  circles  through  the  bark,  one  at  the  foot  of  the 
trunk,  the  other  4  feet  above.  The  bark  is  then  slit  longitudinally 
and  taken  off  in  from  one  to  four  pieces.  (PL  III.)  The  circle  of  bark 
thus  removed  is  called  a  " rim"  or  a  "  coil."  The  first  coil  is  removed 
from  the  standing  tree  because  it  is  easier  to  work  when  the  tree  is 
erect  and  because  it  prevents  the  loss  in  chips  at  the  base  of  the  tree, 
where  the  best  bark  is.  In  felling,  the  woodsman  takes  advantage 
of  the  lay  of  the  land,  of  down  logs,  and  of  gullies,  in  order  that  the 
trunk  may  not  lie  flat  on  the  ground  and  interfere  with  the  removal 
of  the  bark.  Most  tanbark  oak  trunks  are  badly  fire-hollowed,  which 
makes  it  difficult  to  place  them  accurately.  After  the  tree  is  down 
the  small  branches  are  lopped/and  interfering  shrubs  are  brushed  out. 
One  man  then  goes  ahead  "Hnging,"  or  cutting  through  the  bark 
around  the  trunk;  the  second  man  follows,  slits  the  bark,  and  removes 
the  coils.  This  process  is  continued  up  the  trunk  until  the  bark 
becomes  less  than  one-half  inch  thick.  As  the  "coils"  are  taken  off 
they  are  laid  on  the  ground  with  the  inner  or  "flesh"  side  up,  where, 
as  they  become  dry,  they  harden  and  curl  up. 

The  average  woodsman  peels  from  1  to  1J  cords  per  day.  Where 
the  stand  consists  of  trees  with  straight,  clear  trunks  standing  on 
ridges,  an  expert  peeler  can  cut  from  4  to  5  cords  in  a  day.  In  the 
case  of  very  limby  trees  it  is  a  general  practice  to  take  the  bark  off 
only  the  clear  portion  of  the  trunk  and  abandon  much  of  the  remaining 
bark  even  where  it  is  thick.  The  quality  of  such  waste  is  shown  by 
the  analyses  given  in  Table  3. 


12 


CALIFORNIA   TANBARK   OAK. 
TABLE  3. — Analyses  of  bark  wasted  in  abandoned  tops. 


Origin  of  samples. 

Solids  soluble  in  cold  water. 

Solids 
soluble 
in  hot 
water 
only, 
reds. 

Total 
solids. 

Tannin. 

Non- 
tannin. 

Total. 

1.  Sample  taken  3  feet  beyond  last  coil  removed  by 
peelers  

Per  cent. 
17.29 

15.64 

Per  cent. 
13.08 

11.82 

Per  cent. 
30.37 

27.46 

Per  cent. 

Per  cent. 
30.32 

27.56 

2.  Sample  taken  8  feet  beyond  last  coil  removed  by 
peelers 

0.10 

Although  peeling  into  limby  crowns  adds  disproportionately  to  the 
expense  because  of  the  thinner  bark  and  the  extra  trouble  to  get  it, 
nevertheless  waste  could  be  lessened  economically  through  closer 
supervision  of  the  peelers. 

It  is  customary  to  peel  all  the  trees,  even  down  to  poles  from  3  to  8 
inches  in  diameter.  One  or  two  coils  are  taken  from  these  poles 
without  felling  them.  This  practice,  called  "jayhawking,"  also  leads 
to  waste  in  bark.  The  two  coils,  which  can  be  taken  off  without 
cutting  the  tree  down,  do  not  always  include  all  the  bark  worth 
taking.  In  some  districts  "  jayhawked"  trees  are  frequent  with  clear 
trunks  for  20  feet  above  the  last  coil  taken  and  bark  three-quarters 
of  an  inch  thick.  The  quality  of  such  waste  is  shown  by  the  analyses 
given  in  Table  4. 

TABLE  4. — Analyses  of  bark  left  on  "jayhawked"  trees,  southern  Humboldt  County. 


Description  of  tree. 

Diame- 
ter at  1 
foot. 

Total 
height. 

Solids  soluble  in  cold  water. 

Solids 
soluble 
in  hot 
water 
only, 
reds. 

Total 
solids. 

Tannin  . 

Non- 
tannin. 

Total. 

1.  Two  co  Us  taken  by  peelers;  sam- 
ple from  Just  above  second  coil.  . 
2.  One  coil  taken  by  peeler;  sam- 
ple from  just  above  coil 

Inches. 
8 

3.5 
9 

Feet. 
50 

25 
55 

Per  cent. 
13.05 

13.85 

10.12 

Per  cent. 
6.71 

7.15 
6.72 

Per  cent. 
19.76 

21.00 
16.84 

Per  cent. 
0.09 

.44 

Per  cent. 
19.85 

21.44 
16.58 

3.  Two  coils  taken   by  peelers; 
bark,  sample  from  just  above 

TRANSPORTATION. 

The  bark  curls  up  hi  three  weeks  and  is  then  tough  enough  to 
stand  handling.  It  is  "bunched"  or  gathered  together  in  small 
regular  piles.  The  swampers  cut  narrow  sled  roads  through  the 
woods  to  the  bunches  of  bark  and  it  is  sledded  to  the  wagon  road, 
where  it  is  corded  up.  In  some  districts  the  bark  is  carried  out  on 
mule  back,  loaded  on  iron  panniers. 

After  the  bark  is  sledded  a  woodsman  is  sent  through  the  woods  to 
sack  the  chips  and  search  for  bark  which  has  been  overlooked  or 


Bui.  75,  Forest  Service,  U.  S.  Dept.  of  Agriculture. 


PLATE  III. 


** 


Bui.  75,  Forest  Service,  U.  S.  Dept.  of  Agriculture. 


PLATE  IV. 


FIQ.  1.— PEELING  4-Foor  RINGS  OF  BARK  FROM  THE  FELLED  TREE. 


FIG.  2.— BUNCHING  THE  BARK  IN  SMALL  PILES  ALONG  THE  SLED  ROAD. 


Bui.  75,  Forest  Service,  U.  S.  Dept.  of  Agriculture. 


PLATE  V. 


FIG.  L-THE  SKIDWAYS  TO  WHICH  THE  BUNCHED  BARK  is  SLEDDED,  AND  FROM  WHICH 
IT  is  HAULED  TO  THE  RA/LROAD. 


FlQ.  2.-HAULING  THE   BARK  IN   WAGONS  FROM  THE  SKIDWAYS  TO  THE  CARS. 


PRODUCTION   OF   TANBARK. 


13 


covered  up  by  the  tops  of  the  tress,  but  even  with  this  precaution, 
here  and  there  bark  piles  are  left  whenever  the  peelings  are  extensive. 
Chipped  bark,  which  comes  chiefly  from  the  base  or  "rump"  of  the 
tree,  is  the  richest  of  all  in  tannin,  and,  on  account  of  its  greater  weight 
and  smaller  bulk  than  coil  bark,  particularly  desirable.  But  it  is 
much  more  likely  to  be  scattered  and  overlooked  in  the  woods,  and 
it  would  be  better  woods  practice  if  this  bark  were  piled  immediately 
on  peeling  and  sacked  just  before  the  coil  bark  is  bunched.  The  cost 
would  be  no  greater  than- — in  all  probability  not  as  much  as — by  the 
present  method.  The  tannin  quality  of  rump  bark  is  shown  in 
Table  5: 

TABLE  5. — Analyses  of  the  tannin  quality  of  rump  baric. 


Locality. 

Solids  soluble  in  cold  water. 

Solids 
soluble 
in  hot 
water 
only, 
reds. 

Total 
solids. 

Tannin. 

Non- 
tannin. 

Total. 

Southern  Humboldt  County  

Per  cent. 
29.20 
20.89 

Per  cent. 
12.86 
6.97 

Per  cent. 
42.06 
27.86 

Per  cent. 
2.86 
3.26 

Per  cent. 
44.92 
31.12 

Santa  Cruz  County 

On  the  Sonoma  and  Mendocino  coasts  the  tanbark  is  usually  trans- 
ported to  the  ocean  by  the  steam  logging  railways,  which  follow  the 
courses  of  the  numerous  rivers  and  creeks.  These  roads  were  built 
primarily  to  carry  redwood,  but  have  cars  with  frames  for  tanbark. 
The  Mendocino  coast  is  rockbound  and  there  are  no  real  harbors,  but 
only  open  roadsteads  or  half-sheltered  coves.  The  cars  are  run  out 
upon  a  headland,  and  the  frame,  with  its  load,  is  lifted  by  a  steam 
derrick  and  transported  by  a  cable  to  a  schooner  offshore.  A  schooner 
that  carries  200  cords  of  bark  may  be  loaded  thus  in  a  very  short  time. 
Nearly  all  of  the  bark  shipped  by  schooner  from  the  Mendocino  coast 
goes  to  the  San  Francisco  Bay  tanneries. 

Sometimes  tanbark  is  transported  to  the  coast  by  four-horse  wagons, 
which  have  a  capacity  of  from  2  to  4  tons. 

The  bark  delivered  for  shipment  must  be  air-dry  and,  according  to 
the  rules,  must  not  include  any  "paper  bark"  or  "snake  skin" — that 
is,  bark  less  than  half  an  inch  thick.  In  practice,  however,  thin  bark 
is  included  in  the  shipments  without  arousing  protest,  provided  there 
is  not  too  much  of  it.  In  the  hot,  rainless  summers  of  the  Coast  Range 
there  is  no  difficulty  in  meeting  the  requirement  that  the  bark  be 
air-dry.  Bark  rarely  reaches  the  market  in  less  than  from  four  to 
eight  weeks  from  the  tune  of  peeling.  Heavy  bark  loses  from  25  to 
30  per  cent  of  water  in  this  period,  medium  bark  from  30  to  35  per 
cent,  second  growth  and  paper  bark  from  35  to  40  per  cent.  There 
is  also  a  slight  loss,  from  0.5  to  1  per  cent,  due  to  breakage  in  han- 
dling and  shipping. 


14 


CALIFORNIA   TANBARK   OAK. 


The  long  dry  season  of  California  is  highly  favorable  to  the  tanbark 
industry ,  since  it  obviates  precaution  against  rain.  Bark  held  over 
winter  must  be  sheltered,  since  more  than  25  per  cent  of  tannin  is 
leached  out  by  rain  in  one  winter.  Dampness  also  causes  mold, 
which  injures  the  leather  and  is  difficult  to  get  rid  of. 

QUALITY   OF   THE   BARK. 

The  proportion  of  tannin  varies  with  the  part  of  the  tree  from  which 
the  bark  is  taken  and  with  the  local  and  geographical  situation  of  the 
tree.  Old  bark  near  the  base  of  the  trunk  contains  the  highest  pro- 
portion. The  color  of  a  cross  section  of  fresh  bark  is  an  index  of  the 
quality  in  this  respect ;  bark  richest  in  tannin  is  a  deep  red,  while  the 
poorest  is  pale  or  yellowish.  Bark  is  not  considered  ripe  until  it  has 
formed  three  layers,  a  rougher  outer  "ross,"  a  central  "meat,"  and 
an  inner  "fiber."  Before  it  has  divided  thus  the  tannin  content  is 
low.  Trees  in  virgin  stands  arrive  at  this  maturity  at  from  55  to  70 
years  of  age. 

The  variation  in  bark  quality  on  a  typical  tree  is  shown  in  Table  6 : 

TABLE  6. — Analyses  showing  distribution  of  tannin  from  the  base  to  the  top  of  the  tree.1 


Location  of  sample. 

Thick- 
ness of 
bark. 

Solids  soluble  in  cold 
water. 

Solids 
soluble 
in  hot 
water 
only, 
reds. 

Total 
solids. 

Tan- 
nin. 

Non- 
tannin. 

Total. 

Rump 

Incht 
li 
1 

1 
1 

i 

i 

•5. 

>, 
s, 

Per  ct. 
29.20 
25.77 
19.93 
16.13 
19.37 
13.16 
13.21 
10.00 
12.50 
10.82 

Per  ct. 

12.86 
12.72 
10.76 
9.26 
11.63 
9.40 
8.17 
6.78 
9.42 
8.42 

Per  ct. 
42.06 
38.49 
30.69 
25.39 
31.00 
22.56 
21.38 
16.78 
21.92 
19.24 

Per  ct. 
2.86 

Per  ct. 
44.92 
38.49 
30.69 
25.39 
31.16 
22.56 
21.38 
16.78 
21.92 
19.24 

First  "cut  

15  feet 

31  feet  

45  feet 

0.16 

60  feet  

66  feet. 

74  feet 

78  feet.. 

84  feet 

1  Tree  18  inches  in  diameter  4  feet  from  the  ground,  and  96  feet  high,  in  northerly  h'ollow,  southern  Hum- 
boldt  County. 

Sunshine  and  light  increase  the  secretion  of  tannin.  For  this 
reason  the  best  bark  grows  on  ridges,  and  the  southern  districts  yield 
a  richer  product  than  the  northern.  Bark  from  the  Santa  Lucia 
Mountains,  the  southernmost  of  all  the  districts,  is  the  richest  in  the 
market  and  averages  as  high  as  from  20  to  24  per  cent.  According 
to  the  tanners  who  have  used  bark  from  widely  separated  districts, 
that  grown  in  the  "Bald  Hills"  district  in  the  interior,  beyond  the 
influence  of  the  sea  fogs,  is  richer  than  that  from  the  coast,  where  the 
trees  are  shaded  by  redwoods  and  are  in  the  fog  belt.  Bark  from  the 
coast  of  Oregon  is  low  in  tannin,  with  an  average  of  only  12  or  14 
per  cent. 


PROLONGING   THE   SUPPLY. 


15 


Table  7  shows  the  results  of  analyses  of  bark  of  representative  trees 
of  the  various  districts: 

TABLE  7. — Analyses  of  bark  samples  from  different  districts. 


Bald  Hills  districts. 

Solids  soluble  in  cold  water. 

Solids 
soluble  in 
hot  water 
only, 
reds. 

Total 
solids 
extract. 

Tannin. 

Nontan- 
nin. 

Total. 

Thick  bark,  commercial  sample,  Briceland,  Hum- 
boldt  County 

Per  cent. 
24.74 
14.82 
14.90 

15.66 

15.36 

20.51 

22.20 
14.92 
14.00 
16.20 
22.73 

19.08 

21.61 
18.93 
18.24 

Per  cent. 
13.18 
9.60 
11.86 

7.12 
10.02 

11.21 

11.69 
8.89 
6.73 
8.92 
10.07 

9.76 

6.85 
5.40 
9.24 

Per  cent. 
37.92 
24.42 
26.76 

22.72 
25.38 

31.72 

33.89 
23.81 
20.73 
25.  12 
33.80 

28.84 

28.46 
24.33 

27.48 

Per  cent. 
3.08 
1.78 
2.16 

2.52 

1.88 

3.24 

2.87 
1.15 
1.86 
3.76 
1.14 

7.96 

2.14 
2.67 
3.60 

Per  cent. 
41.00 
26.20 

28.92 

25.24 
27.  26 

34.96 

36.  76 
24.96 
22.59 
28.88 
34.94 

36.80 

30.60 
27.00 
30.08 

Thick  bark,  Acorn  region,  llumboldt  County  

Thin  tfark,  Acorn  region,  llumboldt  County  

Between  Low  Gap  and  Summit,  west  of  Ukiah: 
It-foot  tree,  sample  at  3  feet  from  ground,  ridge 
tree 

ly-foot  tree  within  15  feet  of  preceding  

Just  east  of  Coast  Range  summit  (west  of  Ukiah); 

Elk  Creek,  Mendocino  County: 
Thick  bark                                                                •> 

Medium  bark  .               

Thin  bark 

Ridge  tree  in  open,  near  coast  at  Kenny's;  2-foot  tree. 
Ridge  tree  near  coast  at  Kenny's'  2-foot  tree 

South  slope  tree  exposed  to  sun,  Halfway  House, 
Ukiah-Mendocino  Road;  2-foot  tree 

San  Vicente  Creek,  Santa  Cruz  Mountains,  Redwood 
district: 
3-foot  smooth-barked  tree  

Rough-barked  tree  within  10  feet  of  preceding; 
2i-foot  tree 

San  Vicente  Creek,  Santa  Cruz  Mountains,  S.Woot 
tree 

PROLONGING  THE    SUPPLY. 

With  the  disappearance  of  the  bodies  of  tanbark  oak  which  have 
furnished  the  chief  tanning  material  for  the  leather  manufacturing 
industry  on  the  Pacific  coast  the  question  of  the  continuation  of  the 
supply  becomes  very  important.  Since  the  greater  portion  of  the 
standing  tanbark  is  now  confined  to  broken  and  inaccessible  moun- 
tain country,  the  extension  of  transportation  facilities  to  those 
regions  must  exert  a  very  marked  influence  on  its  exploitation  and 
cost.  Railroads  and  wagon  trails  are  being  rapidly  pushed  into  the 
northern  coast  ranges,  and  it  is  probable  that  within  two  or  three 
years  the  rich  belts  of  Mendocino,  Humboldt,  and  Del  Norte  Counties 
will  have  at  least  one  railway  line.  The  utilization  of  second  growth; 
the  introduction  of  more  conservative  methods  in  the  woods,  par- 
ticularly in  connection  with  the  redwood  lumbering  industry;  the 
protection  of  the  forests  from  fire;  and  the  extension  of  the  use  of 
other  products  as  substitutes  for  and  supplements  of  the  bark  of 
this  most  important  tree,  will  all  have  their  influences  on  the  future 
supply. 


16  CALIFORNIA   TANBARK    OAK. 

PROVIDING    FOR    SECOND    GROWTH. 
SPROUT   REPRODUCTION. 

For  the  maintenance  of  the  supply  of  tanbark  on  the  Pacific  coast 
the  second  growth  on  cut-over  areas  offers  by  far  the  most  hope. 
Sprout  reproduction  must  be  encouraged,  since  the  tree  sprouts  very 
readily  and  with  great  persistence.  Sprouts  grow  from  trees  of  prac- 
tically Siuy  age  and  under  a  wide  variety  of  conditions.  Of  greatest 
economic  significance  are  those  which  spring  up  from  the  stumps  of 
trees  felled  for  peeling.  The  sprouts  arise  from  conical  woody  buds 
which  are  formed  under  the  bark  at  the  base  of  the  tree,  and  which 
vary  in  number  from  a  scattering  few  to  crowded  thousands.  The 
sprouts  themselves  vary  in  number;  as  many  as  1,400  have  been 
counted  on  one  large  stump.  The  practice  of  peeling  the  tree  down 
as  far  as  possible,  often  below  ground  level,  in  order  to  obtain  all  the 
rich  and  heavy  rump  bark,  exposes  the  buds  and  prevents  sprouts, 
but  peeling  can  safely  be  carried  down  to  the  surface  of  the  ground 
if  the  peelers  ring  the  bottom  of  the  first  run  instead  of  stripping  off 
the  bark  as  far  down  as  it  can  be  torn.  The  original  number  of 
sprouts  is  reduced  by  natural  processes  in  30  years  to  from  four  to 
eight  of  the  most  vigorous  poles.  The  rate  of  height  growth  is  about 
2  feet  a  year.  By  proper  thinning  this  rate  could  be  accelerated. 

Sprouts  also  come  up  freely  about  the  base  of  fire-injured  and  even 
fire-killed  trees,  which  is  a  great  advantage  where  there  are  frequent 
forest  fires,  as  in  the  tanbark  oak  regions.  They  even  grow  vigor- 
ously from  the  stumps  of  old  trees  which  have  been  weakened  by 
dry  rot  or  fire  and  have  fallen.  The  Stumps  of  such  fallen  veterans 
may  be  a  yard  or  two  in  diameter.  Circles  of  sprouts  about  the  rims 
of  such  stumps  which  have  disappeared  are  often  found  in  the  woods, 
and  the  trunks  of  these  sprouts  are  sometimes  2  feet  in  diameter  at 
4  feet  from  the  ground.  Sometimes  sprouts  will  start  from  the  base 
of  living  trees,  though  this  habit  is  of  slight  commercial  importance. 

Nothing  can  better  illustrate  the  vitality  of  tanbark  oak  than  the 
longevity  of  standing  trees  which  have  been  peeled.  Peeling  is 
usually  done  before  flowering  time,  and  for  the  first  year  afterwards 
the  growth  of  the  tree  is  so  decidedly  checked  that  it  does  not  fruit. 
The  second  year  the  tree  bears  a  full  crop  of  acorns — often  an  exces- 
sively large  crop.  The  woodsmen  call  this  the  "last  kick"  of  the 
tree,  since  in  the  third  year  it  usually  dies.  If  the  tree  stands  exposed 
to  the  full  heat  of  the  sun  it  will  probably  die  the  first  season.  Yet 
there  is  abundant  testimony  that  it  may  continue  to  live  for  a  long 
period — even  10  or  15  years.  The  apparent  anomaly  of  a  tree  con- 
tinuing its  life  functions  with  a  complete  band  of  bark  removed  from 
its  trunk  can  be  explained  by  a  study  of  "jayhawked"  trees  in  the 
field.  Such  trees  were  peeled  either  so  early  in  the  season  or  so  late 


PROLONGING   THE   SUPPLY.  17 

in  the  season  that  the  bark  did  not  part  readily  from  the  wood,  and 
a  very  thin  portion  of  the  inner  bark  and  cambium  layer  adhered  to 
the  wood  and  formed  a  sort  of  film.  This  film  after  one  season  looks 
like  a  thin  ooat  of  brown  varnish.  The  wood  beneath,  however,  is 
greenish  and  pulpy,  suggesting  the  mesophyll  layer  of  a  leaf.  This 
layer  does  not  increase  appreciably  in  thickness. 

REPRODUCTION    BY    SEED. 

No  other  oak  on  the  Pacific  coast  produces  so  heavy  a  crop  of 
acorns  as  tanbark  oak,  but  seedlings,  nevertheless,  are  not  abundant. 
In  the  main,  forest  seedlings  are  found  only  where  a  fallen  tree  has 
made  a  break  in  the  forest  canopy  and  let  in  light.  The  "Bald 
Hills"  country  is  filled  with  hogs  and  cattle,  which  prevent  seedling 
reproduction  by  devouring  the  acorns  and  browsing  the  tender  foli- 
age of  the  young  growth. 

Attempts  at  artificial .  propagation  outside  the  natural  range  of 
tanbark  oak  have  failed.  The  acorns  germinate  in  open  nursery  beds 
in  about  five  weeks.  The  seedlings  come  up  a  little  more  promptly 
in  loam  beds  than  in  adobe,  but  those  in  the  adobe  seem  a  trifle  more 
vigorous  than  the  others.  Sand  beds  germinate  only  2  per  cent  of  the 


Eighty  per  cent  of  the  seeds  planted  in  1902  at  the  California  For- 
estry Station  at  Chico  germinated,  but  not  one  seedling  survived  the 
first  summer,  although  the  soil  conditions  are  favorable.  The  hot, 
dry  climate  of  the  interior  valleys  does  not  furnish  a  normal  environ- 
ment for  tanbark  oak,  and  the  formation  of  plantations  is  practica- 
ble only  where  conditions  are  similar  to  those  of  the  natural  range 
of  the  tre*e. 

SECOND-GROWTH     BARK. 

For  several  years  second  growth  has  been  peeled  in  the  Santa  Cruz 
Mountains,  and  it  is  claimed  by  some  owners  who  superintended  both 
peelings  that  the  yield  of  second  growth  exceeds  that  of  the  virgin 
stand.  There  is  nothing  to  prove  or  disprove  this  assertion,  but  it 
is  probable  that  these  men  did  not  take  account  of  the  fact  that  the 
harvesting  of  the  crop  to-day  is  very  much  closer  and  more  careful 
than  the  peeling  of  the  virgin  timber  from  30  to  50  years  ago,  and 
that  "passed  trees"  of  the  virgin  stand  were  stripped  at  the  sec- 
ond peeling.  Although  it  is  improbable  that  the  yield  of  second 
growth  at  the  end  of  30  years  would  equal  that  of  the  original 
stand,  it  is  sufficiently  heavy  to  make  the  holding  of  cut-over  lands 
profitable  for  repeeling  in  30  years,  when  from  1  to  5  cords  per 
acre  can  be  harvested. 

Table  8  gives  the  yields  of  a  number  of  second-growth  trees  in  the 
Santa  Cruz  Mountains. 

89446°— Bull.  75—11 3 


18 


CALIFORNIA   TANBARK    OAK. 


TABLE  8. — Amount  of  bark  on  second-growth  tan  oak,  age  29  to  31  years,  Santa  Cruz 

Mountains. 


•  Height 
of  tree. 

Diame- 
ter of 
trunk  at 
2  feet. 

Length 
of  peeled 
trunk. 

Diame- 
ter of 
trunk  at 
end  of 
last  coil. 

Thick- 
ness of 
bark  at 
butt. 

Weight 
of  bark, 
green. 

Weight 
of  bark 
dry  (cal- 
culated). 

Feet. 

Inches. 

Feet. 

Inches. 

Inches. 

Pounds. 

Pounds. 

52 

7 

24 

4 

U 

145 

91 

50 

6 

24 

4 

1J 

143 

90 

62 

10 

24 

6 

li 

241 

152 

55 

7 

20 

4 

I* 

125 

79 

65 

9 

28  , 

6 

2 

.  243 

152 

55 

7 

20 

,      5 

11 

120 

76 

62 

8 

-     24 

5 

l| 

158 

100 

62 

7 

24 

5 

I* 

160 

101 

60 

8 

28 

6 

2 

235 

148 

65 

10 

28 

6 

i 

303 

191 

70 

9 

28 

6 

i 

303 

191 

67 

10 

36 

5 

2" 

321 

202 

68 

9 

36 

5 

| 

241 

152 

67 

9 

32 

5 

{ 

208 

131 

65 

8 

32 

5 

177 

112 

QUALITY    OF    SECOND-GROWTH    BARK. 

Tanners  estimate  that  second-growth  bark  will  average  only  10  per 
cent  tannin,  and  when  it  was  first  put  upon  the  market  they  objected 
to  it;  but,  mixed  with  virgin  bark,  it  is  now  used  to  a  considerable 
extent.  It  is  distinguishable  from  virgin  bark  by  its  peculiar  smooth- 
ness both  on  the  outside  and  the  inside;  by  its  brittleness,  due  to  lack 
of  fiber,  especially  toward  the  inside,  where  virgin  bark  is  so  fibrous; 
and  by  its  sappiness  and  light  color. 

Table  9  shows  the  characteristics  of  samples  taken  from  near  the 
bases  of  trees.  The  thinner  bark  higher  Up  would,  of  course,  lower 
the  average. 

It  is  possible  to  produce  a  good  quality  of  leather  by  tlie  use  of 
second-growth  bark  alone,  but  a  large  quantity  is  required  to  offset 
its  low  tannin  content.  The  item  of  labor  is  also  greater,  since  it  costs 
more  to  handle  the  extra  bark. 

TABLE  9. — Analyses  showing  tannin  content  of  tan-oak  bark  taken  from  thr&  'Second- 
growth  trees. 


Locality. 

Height. 

Diame- 
ter of 
wood  at 
1  foot. 

Age. 

Solids  soluble  in  cold  water. 

Solids  sol- 
uble in 
hot  water 
only, 
reds. 

Total 
solids. 

Tannin. 

Nontan- 
nin. 

Total. 

Between  Comptche 
and  Low  Gap,  one  of 
16  sprouts  about 
stump 

Feet. 
Mi 

'40 
60 

Inches. 
2* 

5 
9 

Years. 

7 

24 
30 

Per  cent. 
18.28 

16.22 
14.10 

Per  cent. 

8.28 

10.60 
8.94 

Per  cent. 
26.56 

26.82 
23.04 

Per  cent. 
1.00 

,         -56 
.52 

Per  cent. 
27.56 

27.38 
23.56 

Between  Comptche 
and  Low  Gap  

San  Vicente  Creek, 
Santa  Cruz  Moun- 
tains 

PROLONGING   THE    SUPPLY.  19 

CONSERVATIVE    METHODS    IN    THE    WOODS. 

Redwood  lumbering  has  done  much  to  keep  the  annual  supply  of 
tanbark  steady  and  to  make  remote  stands  accessible.  It  is  the 
practice  of  the  redwood  lumber  companies  to  send  tanbark  crews 
through  the  woods  in  advance  of  the  redwood  logging  crews,  since  the 
firing  of  the  district,  which  always  follows  felling,  to  facilitate  the  get- 
ting out  of  the  redwood  logs  by  wire  cable  and  donkey  engine,  badly 
injures  all  standing  trees,  and  even  if  it  does  not  actually  destroy  the 
tanbark  oak  it  makes  peeling  .difficult  or  impossible. 

GUARDING    AGAINST   FIRE. 

Up  to  the  present  time  no  attention  has  been  paid  to  the  future 
condition  of  the  forestf in  which  peeling  has  been  carried  on.  Yet  the 
introduction  of  conservative  methods  would  prevent  a  very  large 
waste.  Fire,  which  always  accompanies  redwood  logging,  makes  it 
an  economical  policy  to  take  all  the  bark  possible,  whether  the  .tree 
has  reached  maturity  or  not.  Under  conservative  methods  " jay- 
Hawked"  trees,  which  yield  only  from  10  to  60  pounds  of  bark  with 
a  low  tannin  content,  would  in  10  or  20  years  form  profitable  elements 
in  the  new  stand  for  both  bark  and  wood.  Despite  the  custom  of 
taking  all  the  bark  that  can  be  peeled  without  regard  to  whether  it 
is  mature  or  not,  the  maximum  yield  is  never  obtained  under  present 
methods.  Some  trees  which  will  not  for  one  reason  or  another  peel 
readily  in  one  season,  although  they  would  a  year  or  two  later,  are 
sacrificed  in  order  to  chip  a  little  bark  off  their  trunks  or  to  secure  one 
or  more  coils  because  the  trees  are  considered  as  doomed  to  fire  any- 
way. Often  from  70  to  90  per  cent  of  the  bark  in  such  cases  can  not 
be  taken  from  the  tree.  Moreover,  the  fires  kill  very  young  trees,  kill 
sprouts  down  to  the  stumps,  and  seriously  interfere  with  reproduction. 
Under  conservative  management  the  older  trees  would  be  saved  for 
peeling  in  a  favorable  year  and  the  younger  ones  permitted  to  develop 
a  new  stand.  As  tanbark  oak  always  grows  in  mixed  stands,  the 
holding  of  redwood  and  Douglas  fir  lands  for  a  second  crop  would 
give  the  tanbark  oak  the  necessary  fire  protection  and  would  furnish 
a  profitable  element  in  the  later  harvests. 

During  the  rainless  season  in  California,  from  May  to  October,  even 
in  the  foggy  coast  region,  fires  caused  by  logging  crews,  hunters, 
campers,  and  in  the  far  north  coast  ranges  by  thunderstorms,  lead  to 
several  million  dollars  damage  every  year.  These  fires  rarely  kill  tan- 
bark  oak  trees,  but  make  long  vertical  wounds  from  4  to  10  feet  up 
the  sides  of  the  trunks.  On  young  trees  these  injuries  are  often  com- 
pletely covered  by  the  meeting  of  new  bark  growth,  but  with  trees 
more  than  100  years  old  the  sides  of  the' wound  usually  spread.  The 
exposed  wood  rots,  and»sucli  trees,  called  "  goose  pens,"  are  difficult 


20  CALIFORNIA   TANBARK    OAK. 

to  lay  out  accurately  in  felling.  Even  a  slight  injury  to  the  trunk 
permits  the  entrance  of  fungi  which  weaken  the  wood,  and  the  loss  of 
such  trees  in  heavy  snowfalls  is  very  large. 

Trees  on  slopes  or  canyon  sides  are  the  greatest  sufferers;  95  per 
cent  of  the  tanbark  oak  trees  in  those  positions  are  injured  by  fire 
and  80  per  cent  fire  hollowed.  In  the  case  of  ridge  trees,  about  80 
per  cent  are  comparatively  free  from  fire  hollows,  because  a  fire 
traveling  up  a  slope  is  either  running  high  or  going  out  when  it 
reaches  the  top. 

The  most  extensive  destruction  by  fire  in  the  tanbark  oak  belt 
has  probably  been  in  Del  Norte  County,  where  in  former  days  the 
Indians  regularly  fired  the  woods  to  make  better  feed  for  the  deer, 
and  the  packers  set  fires  to  keep  the  trails  open.  Kidge  after  ridge 
has  been  wholly  or  partly  reduced  to  a  low  chaparral  growth,  although 
there  is  evidence  that  a  dense  forest  existed  at  a  comparatively  recent 
date.  A  conservative  estimate  of  the  loss  of  tanbark  by  fire  within 
15  years  in  this  region  is  60,000  cords. 

In  the  second-growth  districts  the  accumulation  of  debris  inside 
the  circles  of  poles  about  the  remains  of  the  parent  stumps  furnishes 
material  for  flames.  Forty  per  cent  of  such  poles  show  serious  injury 
at  the  bases. 

("^TANNIN  EXTRACT  PROCESSES. 

.The  difficulty  of  transportation  has  prevented  the  exploitation  of 
some  of  the  most  productive  tanbark  oak  regions  in  Humboldt  and, 
to  a  smaller  extent,  in  Mendocino  County.  An  attempt  was  made 
to  reduce  this  difficulty  by  grinding  up  the  bark  and  shipping  it  in 
sacks,  but  this  did  not  help  in  the  more  remote  districts  where  the 
weight  was  the  chief  drawback.  In  the  last  few  years  attempts 
have  been  made  to  solve  this  difficulty  by  extracting  the  tannin 
from  the  bark  and  shipping  the  extract. 

Two  methods  have  been  tried  in  California,  the  open-pan  process 
and  the  vacuum-pan  process.  The  open-pan  process  was  tried  in 
southern  Mendocino  County  hi  1900  and  1902,  but  was  abandoned 
because  the  heat  necessary  to  secure  rapid  evaporation  in  concen- 
trating the  mixture  of  ground  bark  and  liquid  was  said  to  scorch 
the  fluid  and  start  fermentation,  so  that  the  barrels  containing  the 
completed  product  often  burst. 

The  vacuum-pan  process  is  used  by  an  extract  plant  at  Briceland, 
Humboldt  County.  The  liquid  from  the  leaching  vats  is  pumped 
into  settling  tanks  in  the  concentrator  house,  and  thence  fed  as 
needed  into  the  "pan"  or  evaporator,  which  is  a  copper  retort  about 
7  feet  in  diameter,  heated  by  steam  pipes  coiled  around  the  base. 
By  heating  the  pan  under  vacuum  the  temperature  of  the  liquid 
during  evaporation  is  kept  from  exceeding*  about  120°  or  130°  F. 


TANNIN   EXTRACT  PROCESSES.  21 

The  vapor  is  condensed  in  a  receptacle  high  enough  above  the  pan 
to  permit  a  34-foot  vertical  waste  pipe.  This  pipe,  kept  full  of  water, 
supplies  a  water  column  sufficient  to  offset  the  atmospheric  pressure 
and  maintain  the  vacuum. 

A  cord  of  dry  bark,  2,200  pounds,  is  reduced  to  50  gallons  of 
extract,  which  weighs  about  550  pounds.  The  extractor  has  a 
capacity  of  12  cords  a  day. 

SUPPLEMENTAL    MATERIALS. 

The  duration  of  the  bark  supply  from  tanbark  oak  will  be  extended 
somewhat  by  the  use  of  other  materials  as  supplements  or  substi- 
tutes. The  superiority  of  the  product  of  the  tanbark  oak  over  all 
other  Pacific  coast  barks  is  due  not  altogether  to  its  high  percentage 
of  tannin,  but  rather  to  the  quality  of  the  particular  tannin  con- 
tained in  it,  and  perhaps  also  to  the  presence  of  certain  other  acids, 
such  as  gallic  and  acetic.  The  value  of  this  combination  is  proved 
by  tanning  experience.  Mixing  imported  tanning  materials,  such 
as  gambier  and  quebracho,  increases  its  effectiveness  and  counter- 
acts some  of  its  undesirable  qualities.  As  tanners  have  learned  the 
use  and  value  of  these  supplementary  agents,  methods  have  been 
more  and  more  adapted  to  them,  until  to-day  they  are  regarded  as 
indispensable  and  the  tanbark  oak  product  is  never  used  alone. 

As  the  accessible  supply  of  tanbark  oak  grows  scarcer  and  dearer, 
the  bark  from  other  species  of  oak  is  occasionally  mixed  with  the 
superior  material.  This  is  especially  the  case  in  the  southern  dis- 
tricts, where  the  tanbark  oak  is  more  nearly  exhausted.  The  barks  of 
the  California  black  oak  and  the  coast  live  oak  run  so  high  in  tannin 
that  if  tannin  content  alone  were  an  index  of  tannage  value  they 
could  compete  with  tanbark  oak.  They  can  not  be  used  alone, 
because  they  will  not  produce  leather  of  goo'd  quality;  the  live-oak 
bark  in  particular  imparts  a  gritty  character  to  the  leather,  which 
ruins  the  knives  of  the  cutters,  but  mixed  in  moderate  quantities 
with  the  better  bark  they  make  possible  a  considerable  saving. 

Alder  bark  is  occasionally  found  in  shipments  of  bark  from  tan- 
bark  oak,  but  the  tree  does  not  grow  in  sufficient  quantity  in  Cali- 
fornia to  be  a  factor  in  bark  supply.  In  the  Mendocino  woods  the 
chinquapin  is  often  peeled,  but  it  contains  so  little  tannin  that  it  is 
practically  worthless.  Moreover,  it  is  very  fibrous  and  tough,  which 
makes  it  difficult  for  the  smaller  tanbark  mills  to  handle. 

Analyses  of  average  bark  samples  from  the  main  trunks  of  the 
important  California  trees  are  given  in  Table  10.  Some  of  these 
have  never  been  subjected  to  commercial  experiment. 


22  CALIFORNIA   TANBARK    OAK. 

TABLE  10. —  Tannin  analyses  of  bark  of  the  more  important  forest  trees  of  the  Pacific  coast. 


Species. 

Locality. 

Soluble  solids. 

Insoluble 
solids, 
reds. 

Total 
solids. 

Tannin. 

Xontan- 
nin. 

Total. 

California  black  oak  (Quer- 
cus  calif  or  nica). 
California  black  oak  

Vaca  Mountains,  So- 
lano  County. 
Briceland,  Humboldt 
County. 
Berkeley 

Per  cent. 
10.00 

10.16 
18.76 
7.92 

6.67 

12.18 

6.56 
11.97 
7.07 
6.20 
7.60 

8.60 
1.45 

15.58 
14.11 
13.45 

9.03 
17.52 

7.15 

10.80 
14.40 
2.50 

1.76 
3.91 

Per  cent. 
10.25 

7.88 
9.40 
5.88 

2.83 
10.18 

5.19 
11.28 
4.93 
4.16 
4.34 

12.00 
3.09 

10.46 
2.85 
3.99 

4.59 
6.24 

5.25 
3.46 
6.56 
2.74 

5.72 
5.85 

Per  cent. 
20.25 

18.04 
28.16 
13.80 

9.50 
22.36 

11.66 
23.25 
12.00 
10.36 
11.94 

20.60 
4.54 

26.04 
16.96 
17.44 

13.62 
23.76 

12.40 
14.26 
20.96 
5.24 

6.48 
7.76 

Per  cent. 
0.95 

.32 
1.48 
1.20 

1.64 
.80 

1.00 
1.55 
.36 
1.00 
.64 

1.68 
.00 

.97 
2.60 
3.72 

.74 
1.60 

.42 
1.32 
2.42 
.10 

.59 
1.58 

Per  cent. 
21.20 

18.36 
29.64 
15.00 

11.14 
23.16 

12.66 
24.80 
12.36 
11.30 

12.  08 

22.  28 
4.54 

27.  Gl 
19.  50 
21.  16 

1^.36 
25.  36 

12.  82 
15.58 
23.38 
5.34 

7.07 
9.34 

California  live  oak  (Quercus 
agrifolia). 
Highland  oak  (Quercus  wis- 
lizeni). 
Highland  oak 

Vaca  Mountains,  So- 
lano  County. 
Southern  Mendocino.  . 
Vaca  Mountains,  So- 
lano  County. 
South  central  Mendo- 
cino. 
Visalia 

Canyon  live  oak,  maul  oak 
(Quercus  chrysolepis). 
Canyon  live  oak  

California  white  oak  (Quer- 
cus lobata). 
Pacific  post  oak  (Quercus 
garryana). 
Pacific  post  oak  

Southern  Humboldt  .  . 

South  central  Mendo- 
cino, "Bald  Hills." 
Southern  Humboldt  .  . 

Mendocino  coast  . 

Western  chinquapin  (Cast- 
anopsis  chrysophylla). 
Red  alder  (Alnu-s  oregona)... 
California    yellow    willow; 
western    black     willow 
(Salix  lasiandra). 
California     laurel     (  Umbel- 
lularia  californica). 
Monterey  pine  (Pinus  radi- 
ata). 
California      swamp      pine 
(Pinus  muricata). 
Lowland  fir  (Abies  grandis) 

Berkeley 

Briceland 

Berkeley  (cult.) 

Mendocino  coast 

...do 

Sitka  spruce  (Picea  sitchen- 
sis). 
Douglas    fir    (Pseudotsuga 
taiifolia). 
Western    hemlock    (  Tsuga 
heterophylla). 
Western  hemlock 

do 

Southern  Humboldt  .  . 
Mendocino  coast  

Noyo   River,  Mendo- 
cino coast. 
Mendocino  coast  

do 

Redwood  (Sequoia  semper- 
virens)  bark. 
Redwood,  sapwood 

Redwood,  heartwood  

do  

POSSIBILITIES  OF  UTILIZING  THE  WOOD. 

The  tanbark  oak  peeled  since  1850  is  equal  to  more  than  2,000,000 
cords  of  firewood.  But,  chiefly  on  account  of  the  difficulty  of  trans- 
portation, little  of  this  amount,  perhaps  5  per  cent,  has  been  used  as 
fuel.  Yet  the  wood  has  such  particular  value  for  special  purposes 
that  it  is  quoted  in  San  Francisco  at  from  $12  to  $18  per  cord,  a  price 
much  higher  than  that  of  any  other  California  oak.  The  wood  burns 
up  very  completely  with  little  smoke.  The  United  States  mint 
at  San  Francisco  uses  it,  and  there  is  a  steady  demand  by  the  bakers 
of  that  city.  The  full  possibilities  of  the  wood  for  lumber  can  be  deter- 
mined only  by  experiments  in  sawing  and  seasoning  and  by  strength 
tests,  but  its  availability  for  some  purposes  is  undoubted.  About 
400,000,000  feet  have  been  utterly  lost  so  far,  and  about  627,000,000 
feet  are  still  standing.  To  utilize  the  log  for  lumber,  it  must  be  cared 
for  immediately  after  peeling.  Only  the  redwood  logging  companies 
possess  facilities  for  yarding  and  sawing  the  tanbark  oak;  yet  since  the 
peeling  time  comes  at  the  height  of  their  busy  season,  any  proposal 


CONCLUSIONS.  23 

to  depart  from  the  custom  of  abandoning  the  tanbark  oak  log  as  use- 
less does  not  meet  with  favor.  Moreover,  their  milling  machinery 
is  not  well  adapted  to  sawing  oak  logs,  and,  for  satisfactory  work, 
the  installation  of  special  plants  would  be  necessary. 

Country  wagon  makers  in  the  Coast  Range  constantly  use  tanbark 
oak  for  repair  work  and  believe  it  superior  to  all  other  wood  for  felloes. 

The  wood,  unlike  some  others,  such  as  the  eastern  chestnut,  has  no 
value  whatever  as  a  tanning  agent. 

CONCLUSIONS. 

(1)  The  bark  of  tanbark  oak  is  one  of  the  most  valuable  tanning 
agents  known  for  the  production  of  heavy  leather.     Bark  from  the 
interior  ridges  and  southern  districts  is  prized  more  than  bark  from 
the  deep  redwood  belt  or  from  northern  districts,  because  it  averages 
higher  in  tannin. 

(2)  The  Pacific  coast  tanbark-oak  belt  contains  enough  standing 
tanbark  at  the  present  time  to  supply  the  needs  of  California  tanneries 
at  their  present  rate  of  consumption  for  47  years. 

(3)  There  should  be  more  systematic  methods  in  peeling  and  a 
greater  proportion  of  the  bark  above  the  clear  trunk  should  be  taken. 
Bark  from  one-half  to  one-fourth  inch  thick  ^should  be  saved  when- 
ever possible.     Chipped  bark  should  be  sacked  before  bunching  the 
coil  bark.     Trees  with  bound  bark  should  be  temporarily  passed, 
and  not  mutilated  or  sacrificed.     Tops  should  be  burned  in  the  win- 
ter following  cutting  to  prevent  the  destruction  of  young  growth  and 
of  passed  trees  by  wild  forest  fires. 

(4)  Tanbark    oak   is   surpassed    in    reproductive   powers    by  no 
other  forest  trees  in  western  America,  except  the  redwood,  and  it 
stands  very  close  to  that  species.     A  crop  of  sprouts  will  normally 
arise  from  the  base  of  every  peeled  stump.     In  order  to  favor  this 
crop,  peelers  should  ring  the  trunk  at  base  and  not  break  the  coil 
down  below  the  surface  of  the  ground.     These  sprouts  will  give  rise 
to  " second-growth"  poles  which  are  commercailly  profitable  to  peel 
within  25  or  35  years. 

(5)  Standing  trees  after  being  peeled  may  live  on  indefinitely,  but 
they  never  produce  a  second  bark  which  has  any  commercial  value. 

(6)  The  wood  is,  for  the  most  part,  allowed  to  rot  on  the  ground. 
Prompt  care  would  tend  to  obviate  its  greatest  weakness,  checking 
in  seasoning,  and  it  can  certainly  be  applied  to  some  of  the  uses  for 
which  oak  wood  is  prized,  and  a  stupendous  annual  waste  thereby  be 
eliminated. 

(7)  Forest  fires  are  a  source  of  great  annual  loss,  and. cooperative 
measures  should  be  taken  by  the  State  of  California,  the  coast  counties, 
the  redwood  companies,   the  tanbark  companies,   and  cattle-range 
owners  to  reduce  the  danger  from  fire.     A  conservative  treatment 
of  the  redwoods  to  obtain  a  continuous  crop  will  be  of  like  advantage 
to  the  tanbark  oak  mixed  with  it. 


PART  II.— UTILIZATION  OF  THE  WOOD  OF  TANBARK  OAK, 

By  H.  S.  BETTS. 
TANBARK-OAK   LUMBER,   v 

While  the  wood  of  tanbark  oak  is  sometimes  used  for  fuel,  it  is 
more  generally  burned  in  the  redwood  logging  operations,  or  left  to 
rot  in  the  woods.  The  object  of  this  study  is  to  bring  to  the  atten- 
tion of  west  coast  hardwood  users  and  the  owners  of  tanbark-oak 
stumpage  the  possibility  of  using  tanbark-oak  lumber. 

The  largest  part  of  the  hardwoods  used  on  the  Pacific  coast  is 
imported  from  the  eastern  part  of  the  United  States.  From  1899  to 
1906  there  was  an  increase  in  the  price  of  hardwoods  in  the  East  of 
from  25  to  65  per  cent.  These  conditions  have  been  reflected  in  the 
western  hardwood  markets.  Not  only  are  the  prices  of  most  kinds 
of  hardwood  going  up  rapidly,  but  in  some  cases  certain  species  are 
difficult  to  obtain  at  any  price.  This  scarcity  is  due  not  to  any  local 
condition,  but  to  the  general  shortage  of  hardwood  timber.  The 
high  price  is  due  to  the  eastern  market  price,  to  which  must  be  added 
about  85  cents  per  hundredweight  in  freight  charges,  or  an  advance 
of  from  $24  to  $36  or  even  $40  per  thousand  board  feet. 

Yet  tanbark  oak  furnishes  a  fair  quantity  of  good  material.  For 
instance,,  the  average  yield  of  bark  is  from  1J  to  2^  cords  per  acre. 
If,  as  seems  reasonable,  there  are  800  feet  board  measure  of  lumber 
for  every  cord  of  bark,  the  yield  in  lumber  would  be  from  1,000  to 
1,760  feet  board  measure  per  acre.  Exceptionally  fine  stands  yield 
as  high  as  8  cords  of  bark  to  the  acre,  which  would  mean  6,400  board 
feet  of  lumber. 

APPEARANCE    AND   CHARACTERISTICS   OF  THE   WOOD. 

The  wood  of  tanbark  oak,  like  that  of  other  oaks,  is  porous  and 
has  the  characteristic  strongly  marked  medullary  rays.  In  color  it 
is  light  brown,  faintly  tinged  with  red.  When  the  wood  is  first  cut 
the  sap  wood  is  somewhat  lighter  in  color  than  the  heartwood,  but 
after  a  few  weeks'  exposure  to  the  air  the  two  become  very  similar 
in  appearance. 

Exact  knowledge  of  the  rate  of  growth  of  tanbark  oak  is  very 
limited.  Seven  forest-grown  trees  near  Sherwood,  Cal.,  showed  varia- 
tions of  from  10  to  20  rings  per  inch.  The  trees  were  from  14  to  27 
inches  in  diameter  2  feet  above  the  ground.  Even  on  the  stump  the 
24 


Bui.  75,  Forest  Service,  U.  S.  Dept.  of  Agriculture. 


PLATE  VI. 


FIG.  1.— MACHINE  AND  METHOD  USED  FOR  TESTING  SMALL  BEAMS. 


FIG.  2.— SEASONING  CHECKS  IN  THE  BUTT  OF  A  TANBARK  OAK  LOG  THAT  HAS  BEEN 
SUBJECTED  TO  THE  SEVERE  TEST  OF  BEING  TURNED  UP  AND  EXPOSED  TO  THE  HOT 
CALIFORNIA  SUN  FOR  Six  WEEKS. 


Bui.  75,  Forest  Service,  U.  S.  Dept.  of  Agriculture. 


PLATE  VII. 


FIG.  1.— TANBARK  OAK  LUMBER  FOR  CAR  CONSTRUCTION. 


FIG.  2.— TANBARK  OAK  BOARDS  AIR  DRYING. 


APPEARANCE   AND   CHARACTERISTICS. 


25 


annual  rings  are  difficult  to  distinguish,  since  the  temperature  changes 
from  season  to  season  are  not  marked  enough  to  form  the  distinct 
bands  of  spring  and  summer  wood  common  in  eastern  oaks.  In  the 
case  of  the  lumber,  it  becomes  impracticable  to  attempt  to  obtain  the 
rate  of  growth  of  different  pieces. 

STRENGTH. 

The  material  used  in  the  tanbark  oak  tests  was  divided  into  three 
classes  or  shipments,  differing  in  the  age  of  the  trees  and  the  season 
of  cutting.  The  first  two  shipments  were  selected  in  the  summer 
during  the  peeling  season,  and  represented  in  the  first  shipment  the 
larger  and  more  mature  trees  of  the  stand,  and  in  the  second  shipment 
the  smaller  and  younger  trees.  The  third  shipment  was  felled  in 
October  and  represented  the  same  wood  as  that  obtained  in  the  first 
shipment,  but  felled  in  the  season  when  the  bark  was  tight,  or  when 
the  sap  was  not  running. 

The  strength  of  the  wood  in  several  conditions  of  seasoning  is 
shown  in  Table  11.  The  three  shipments  had  practically  the  same 
strength  and,  therefore,  were  combined  in  the  table. 

TABLE  11. — Strength  of  small  clear  pieces  of  tanbark  oak,  green,  air-dry,  and  kiln-dry, 

size  2  by  2  inches  in  section. 

GREEN. 


• 

Bending. 

Num- 
ber of 
tests. 

Mois- 
ture 
con- 
tent. 

Weight  per 
cubic  foot. 

Fiber 
stress  at 
elastic 
limit 
per 
square 
inch. 

Modu- 
lus of 
rupture 
per 
square 
inch. 

Modu- 
lus of 
elastic- 
ity per 
square 
inch. 

Elastic 
resil- 
ience 
per 
cubic 
inch. 

As 
tested. 

Oven 
dry.  i 

Average                             

256 
26 
26 

Per  ct. 

89.5 
110.5 
65.5 

Pounds. 
66.5 
71.7 
60.3 

Pounds. 
43.1 
48.1 
38.2 

Pounds. 
6,576 

8,283 
4,869 

Pounds. 
10,  707 
12,880 
8,632 

1,000 
pounds. 
1,678 
2,251 
1,203 

Inch 
pounds. 
1.49 
2.35 
.83 

High  10  per  cent 

Low  10  per  cent  

AIR-DRY  (10  TO  20  PER  CENT  MOISTURE). 


Average                            

567 

14.0 

45.2 

43.2 

9,080 

15,  512 

2,083 

2.27 

High  10  per  cent 

57 

17.4 

51.7 

50.5 

11,901 

20,342 

2,771 

3.45 

Low  10  per  cent                 

57 

10.5 

39.5 

37.1 

6,482 

11,625 

1,511 

1.19 

KILN-DRY  (5  TO  10  PER  CENT  MOISTURE). 


Average 

31 

9.6 

45.4 

43.9 

9,289 

17,693 

2,292 

2.17 

High  10  per  cent                         

3 

'     10.0 

50.2 

48.8 

12,287 

22,  417 

2,966 

3.41 

Low  10  per  cent 

3 

8.8 

40.9 

39.5 

6,600 

13,  077 

1,642 

1.11 

26 


CALIFORNIA   TANBARK    OAK. 


TABLE  11. — Strength  of  small  dear  pieces  of  tanbark  oak,  green,  air-dry,  and  kiln-dry, 
size  2  by  2  inches  in  section — Continued. 


GREEN. 


Compression  parallel  to 
grain. 

Compression  perpendic- 
ular to  grain. 

Shearing. 

Num- 
ber of 
tests. 

Mois- 
ture 
con- 
tent. 

Crushing 
strength 
per 
square 
inch. 

Num- 
ber of 
tests. 

Mois- 
ture 
con- 
tent. 

Strength 
at  elastic 
limit,  per 
square 
inch. 

Num- 
ber of 
tests. 

Mois- 
ture 
con- 
tent. 

Strength 
parallel 
to  grain 
per 
square 
"  inch. 

Average  

237 
24 
24 

Per  ct. 

86.8 
105.4 
64.8 

Pounds. 
4.845 
5,819 
3,711 

244 
24 
24 

Per  ct. 
77.9 
95.3 
59.7 

Pounds. 
1,355 
1,964 
926 

221 
22 
22 

Per  ct. 
83.1 
103.. 
56.1 

Pounds. 
1,414 
1,685 
1.075 

High  10  percent.    . 

Low  10  per  cent  

AIR-DRY  (10  TO  20  PER  CENT  MOISTURE). 


Average  

406 

14.4 

8,172 

316 

13  4 

1  656 

204 

13  3 

1  %0 

High  10  per  cent 

41 

17  7 

10  405 

32 

16  9 

2  343 

20 

16  9 

2  402 

Low  10  per  cent  

41 

10.7 

6,265 

32 

10  5 

1  238 

20 

10  6 

1  585 

KILN-DRY  (5  TO  10  PER  CENT  MOISTURE). 


Average                            * 

28 

9.4 

9,398 

26 

9  5 

1  818 

22 

9  0 

2  037 

High  10  per  cent 

3 

10  0 

10  737 

3 

10  0 

2  293 

2 

10  0 

2  384 

Low  10  per  cent.  . 

3 

8.2 

8,047 

3 

8  4 

l'366 

2 

7  3 

1  669 

1  The  values  in  this  column  are  based  on  a  shrinkage  of  18  per  cent  volume.    The  fiber  saturation  point 
is  taken  as  30  per  cent  moisture. 

Clear,  straight-grained  specimens  free  from  defects  are  needed  in 
determining  the  strength  of  the  wood  itself.  The  results  of  tests 
made  on  this  class  material  can  also  be  used  for  comparison  with 
similar  tests  on  other  kinds  of  wood.  Pieces  2  by  2  inches  in  section 
have  been  found  weh1  suited  to  tests  of  this  kind.  For  bending,1 
they  are  cut  about  30  inches  long,  and  for  compression  parallel  to 
the  grain  and  compression  perpendicular  to  the  grain,  from  6  to  10 
inches  long.  The  blocks  for  shear  parallel  to  the  grain  are  cut  with 
a  projecting  lip  that  is  sheared  off  under  test.  In  making  a  bending 
test  the  beam  is  supported  at  the  ends  and  loaded  at  the  middle. 
The  supports  for  the  beam  are  on  the  weighing  platform  of  the  test- 
ing machine,  so  that  the  load  on  the  beam  can  be  determined  at  any 
time  during  the  test.  This  load  is  applied  by  a  crosshead  which 
can  be  forced  down  on  the  test  specimen  by  means  of  heavy  screws 
turned  by  a  train  of  gears.  The  deflection  or  bending  of  the  beam  is 
measured  by  an  apparatus  (PL  VIII,  fig.  1 )  consisting  of  a  light  steel 
frame  on  which  is  mounted  a  movable  pointer.  In  making  a  test, 
the  frame  is  rested  on  two  nails  driven  into  the  beam  near  the  ends 
and  the  pointer  attached  to  the  center  of  the  beam  in  such  a  way 


1  For  a  detailed  description  of  methods  used  in  the  tests,  see  Forest  Service  Circular  38  (revised),  Instruc- 
tions to  Engineers  of  Timber  Tests. 


APPEARANCE   AND    CHARACTERISTICS.  27 

that  it  moves  over  a  graduated  arc  when  the  beam  bends,  and  thus 
shows  the  amount  of  bending. 

The  test  is  begun  by  loading  the  beam  with  about  one-twentieth 
of  the  probable  breaking  load  and  noting  the  deflection.  The  load  is 
then  increased  by  a  certain  increment  which  is  recorded  with  the  cor- 
responding deflection,  and  the  process  continued  until  the  beam  breaks. 
The  results  of  tests  on  beams  of  various  sizes  are  reduced  to  a  unit 
basis,  so  that  direct  comparisons  as  to  strength  and  stiffness  can  be 
made  between  pieces  of  different  sizes  of  the  same  or  of  different 
species  of  wood. 

In  computing  the  results,  the  breaking  strength  is  represented  by 
11  modulus  of  rupture,"  the  stiffness  by  "  modulus  of  elasticity,"  the 
load  the  material  will  carry  without  taking  a  set  by  "  fiber  stress  at 
the  elastic  limit,"  and  the  ability  to  withstand  shock  without  taking 
a  set  by  "  elastic  resilience." 

Tests  in  compression  parallel  with  the  grain  are  made  by  crushing 
the  specimens  endwise  as  they  stand  upright  on  the  platform  of  the 
testing  machine.  In  the  case  of  compression  perpendicular  to  the 
grain,  the  tests  are  made  by  placing  a  piece  of  metal  2  inches  wide 
across  the  test  specimen  as  it  lies  flat  on  the  platform  of  the  machine 
and  pressing  the  piece  of  metal  against  the  block  of  wood  by  means 
of  the  crosshead  of  the  machine.  This  test  is  carried  only  slightly 
beyond  the  elastic  limit  of  the  wood  under  test,  as  loading  beyond 
that  point  has  at  present  no  significance.  The  action  is  similar  to 
that  of  a  rail  on  a  tie. 

In  making  a  shearing  test  the  block  is  clamped  firmly  in  a  frame 
with  the  lip  projecting.  The  frame  is  placed  on  the  platform  of  the 
machine  and  the  lip  sheared  off  by  means  of  a  sliding  plate  applied 
against  the  upper  surface  of  the  lip  and  parallel  to  the  gram. 

Table  1 1  shows  the  oven-dry  weight  of  tanbark  oak  to  be  about 
43.2  pounds  per  cubic  foot.  Air-dry  tanbark  oak,  containing  15  per 
cent  moisture,  weighs  about  50  pounds  per  cubic  foot,  or  4,160 
pounds  per  1,000  board  feet.  This  weight  is  about- the  same  as  that 
of  white  oak  and  is  somewhat  higher  than  that  of  red  oak. 

The  average  bending  strength  (modulus  of  rupture)  of  green  tan- 
bark  oak  is  10,707  pounds  per  square  inch,  and  the  average  crushing 
strength,  4,845  pounds  per  square  inch.  The  results  of  similar  tests 
on  several  kinds  of  hickory  by  the  Forest  Service,  including  pignut, 
shagbark,  mockernut,  big  shellbark,  nutmeg,  and  water  hickory 
show  a  bending  strength  of  from  9,200  pounds  per  square  inch  for 
green  nutmeg  hickory  to  11,450  pounds  per  square  inch  for  green 
pignut  hickory.  The  average  oven-dry  weight  of  pignut  hickory  is 
about  51  pounds  per  cubic  foot. 

Such  tests  as  have  been  made  on  eastern  white  and  red  oaks  indi- 
cate that  tanbark  oak  in  bending  and  crushing  strength  ranks  about 
the  same  as  white  oak  and  is  somewhat  superior  to  red  oak. 


28  CALIFORNIA   TANBARK    OAK. 

Data  are  not  available  for  a  comparison  of  the  toughness  and  stiff- 
ness of  tanbark  oak  and  the  eastern  oaks  and  hickories. 

Table  11  shows  a  considerable  increase  in  the  strength  values  of 
the  air-dry  material  over  the  green,  and  a  still  further  increase  in 
these  values  for  the  kiln-dry  material. 

In  compression  perpendicular  to  the  grain,  green  tanbark  oak  has 
an  average  strength  at  the  elastic  limit  of  1,355  pounds  per  square 
inch.  Green  Douglas  fir  has  an  average  strength  of  651  pounds  per 
square  inch. 

In  shearing  strength  air-dry  tanbark  oak  shows  an  average  of 
1,960  pounds  per  square  inch.  Douglas  fir  has  an  average  shearing 
strength  of  770  pounds  per  square  inch  for  air-dry  pieces. 

Douglas  fir  would,  of  course,  be  expected  to  have  lower  strength 
values  than  a  hardwood  like  tanbark  oak.  The  comparison  is  used 
because  such  tests  on  other  hardwoods  have  not  yet  been  made. 

SEASONING. 

A  number  of  the  logs  selected  for  testing  purposes  were  sawed  into 
boards  for  a  seasoning  test.  Fifty  1-inch  boards  were  put  through  a 
commercial  dry  kiln  of  the  moist-air  type  in  San  Francisco.  The 
results,  while  encouraging  as  regards  the  behavior  of  tanbark-oak 
lumber  in  a  moist-air  kiln,  were  not  satisfactory,  owing  to  the  imperfect 
regulation  of  the  kiln  and  consequent  daily  variations  in  temperature 
and  humidity.  After  40  days  in  the  kiln  a  classification  of  the  lumber 
gave  the  following: 


Number. 

Per  cent. 

Good  boards                                                                                                         

28 

56 

Boards  slightly  warped 

12 

24 

Boards  checked  at  ends  ...            .                                                 

4 

8 

Boards  badly  checked 

6 

12 

The  average  temperature  of  the  kiln  was  only  85°  F.  for  the  40 
days,  whereas  it  should  have  been  at  least  110°  F.  The  loss  in  sea- 
soning eastern  oak  for  vehicle  stock  is  placed  at  about  10  per  cent. 

The  method  of  seasoning  used  by  a  lumber  company  which  owns 
considerable  tanbark-oak  stumpage  that  it  is  preparing  to  put  on  the 
market  in  the  form  of  flooring  is  as  follows :  The  logs  as  soon  as  con- 
venient after  they  come  in  from  the  woods  are  cut  into  IJ-inch 
material.  This  is  then  carefully  piled  in  the  open  yard,  with  sticks 
every  18  inches,  and  allowed  to  dry  from  3  to  6  months.  It  is  finally 
kiln  dried  from  30  to  40  days  at  a  temperature  not  to  exceed  110° 
F.,  when  the  boards  are  ready  to  be  made  into  flooring.  The  kiln  used 
is  of  the  blower  type.  The  results  obtained  in  drying  tanbark  oak  by 
this  method  have  been  very  satisfactory.  It  should  be  remembered 
that  the  trees  in  this  case  were  cut  during  the  peeling  season  (May  to 


Bui.  75,  Forest  Service,  U.  S.  Dept.  of  Agriculture. 


PLATE  VIII, 


FIQ.  1.— TANBARK  OAK  FLOORING,  AND  THE  METHOD  OF  STORING  AND  SORTING  IT. 


FIG.  2.— TANBARK  OAK  FLOORING  READY  FOR  SHIPMENT  FROM  THE  MILL. 


Bui.  75,  Forest  Service,  U.  S.  Dept.  of  Agriculture. 


PLATE  IX. 


TRANSVERSE  SECTION  OF  A  2-YEAR-OLD  TWIG  OF  TANBARK  OAK,  SHOWING  TANNIN 
(DARK  STREAKS  AND  AREAS)  IN  THE  PITH,  PITH  RAYS,  AND  BARK.  MAGNIFIED  30 
DIAMETERS. 


Bui.  75,  Forest  Service,  U.  S.  Dept.  of  Agriculture. 


PLATE  X. 


FIG.  1  .—TRANSVERSE  SECTION  OF  A  S-YEAR-OLD  TWIG  OF  TANBARK  OAK,  SHOWING  THE 
DISTRIBUTION  OF  TANNIN  IN  THE  PITH  AND  PITH  RAYS.    MAGNIFIED  30  DIAMETERS. 


FIG.  2.— LONGITUDINAL  RADIAL  SECTION  OF  A  S-YEAR-OLD  TWIG  OF  TANBARK 
OAK,  SHOWING  THE  TANNIN  IN  THE  PITH  AND  PITH  RAY  CELLS.  MAGNIFIED  30 
DIAMETERS. 


OCT29  1914 

Division  of  Forestry- 
University  of  California 


SEASONING.  29 

October) .  It  is  very  probable  that  winter-cut  lumber  could  be  sea- 
soned with  less  loss  of  material. 

Some  of  the  boards  and  planks  sawed  from  the  logs  selected  for 
testing  were  piled  under  shelter  and  seasoned  for  about  two  years, 
when  they  were  in  the  same  condition  as  regards  warping  and  check- 
ing as  is  usually  found  in  eastern  oaks  similarly  handled.  Some  of 
the  lumber  showed  a  tendency  to  a  "blue  rot,"  apparently  caused 
by  too  close  piling,  since  this  defect  was  remedied  by  a  wider  piling 
that  gave  more  circulation  of  air. 

In  the  case  of  some  200  pieces  for  mechanical  tests  (2  by  2  by  30 
inches),  cut  from  material  seasoned  under  shelter  for  two  years  and 
then  kiln  dried,  the  pieces  showed  practically  no  checking.  The 
sides  of  the  pieces  were  slightly  depressed  in  a  few  instances,  but  on 
the  whole  their  condition  was  excellent. 

All  things  considered,  the  seasoning  of  tanbark  oak  seems  to  offer 
little,  if  any,  more  difficulty  than  is  experienced  with  eastern  oaks. 

SHRINKAGE.     ^) 

In  order  to  determine  the  amount  of  shrinkage  in  tanbark  oak, 
62  pieces  (2  by  2  by  10  inches)  were  dried  out  slowly  from  a  green 
to  an  oven-dry  condition.  The  pieces  were  selected  so  that  two 
sides  were  tangential  to  the  annual  rings.  They  were  weighed  and 
measured  at  intervals  for  a  period  of  about  one  year.  The  drying 
was  carried  on  first  in  a  warm  room  and  finally  in  an  oven. 

When  a  piece  of  green  or  wet  wood  is  dried,  no  change  in  dimen- 
sions takes  place  until  a  point  called  the  fiber-saturation  point1 
(generally  in  the  neighborhood  of  30  per  cent  moisture)  is  passed. 
The  wood  then  begins  to  shrink  in  cross-sectional  area  and  continues 
to  do  so  uniformly  with  the  removal  of  moisture  until  it  is  bone  dry. 
The  longitudinal  shrinkage  is  so  small  as  to  be  negligible.  Generally, 
the  heaviest  wood  shrinks  the  most  and  sapwood  shrinks  more  than 
heartwood  of  the  same  specific  gravity.  Shrinkage  is  greater  in  the 
circumferential  than  in  the  radial  direction. 

The  results  of  the  shrinkage  tests  on  tanbark  oak  showed  an 
average  shrinkage  in  volume  of  18  per  cent 2  when  the  pieces  were 
dried  from  a  green  to  an  oven-dry  condition.  Of  this  amount  about 
6  per  cent  is  radial  shrinkage  and  about  12  per  cent  tangential.  •  Air- 
dry  wood  generally  contains  about  15  per  cent  moisture,  so  that  the 
shrinkage  from  the  green  to  the  air-dry  state  is  only  about  half  that 
from  the  green  to  the  absolutely  dry  state. 

The  average  shrinkage  in  volume  with  red  oak  when  dried  from  a 
green  to  an  oven-dry  state  is  about  the  same  as  with  tanbark  oak. 
Both  woods  vary  considerably. 

1  For  a  full  discussion  of  the  fiber-saturation  point,  see  Forest  Service  Circular  108,  The  Strength  of  Wood 
as  Influenced  by  Moisture,  by  H.  D.  Tiemann. 

2  This  figure  is  based  on  dry  volume. 


30  CALIFORNIA   TANBARK    OAK. 

HARDWOODS   USED   ON   THE   COAST. 

The  hardwoods  at  present  used  in  the  Pacific  coast  States  come 
from  many  foreign  markets,  and  only  a  very  small  proportion  of 
them  are  local  woods.  From  the  Eastern  States  are  imported  oak, 
ash,  hickory,  maple,  cherry,  basswood,  black  walnut,  tulip  poplar, 
birch,  and  elm;  from  Honduras,  mahogany;  from  Mexico,  Mexican 
mahogany,  prima  vera,  or  jenizero;  from  Hawaii,  koa;  from  Aus- 
tralia, iron  bark  (one  of  the  eucalypts)  and  red  bean;  and  from 
Japan,  Siberian  oak. 

The  hardwoods  from  the  Eastern  States  come  for  factory  use  in 
the  rough  or  ' i club  "  form;  for  the  vehicle  industry  as  roughly  finished 
parts,  such  as  spokes,  hubs,  bent  rims,  and  sawed  felloes;  and  for 
cooperage  as  rough  staves  and  heading.  The  rest  are  in  the  form  of 
1-inch  and  2-inch  boards  and  3  to  6  inch  planks  from  6  to  16  inches 
wide  and  from  10  to  30  feet  long.  A  small  proportion  comes  in  the 
form  of  squared  timbers  up  to  20  by  20  inches  by  24  feet  long.  This 
is  for  special-order  work.  The  Mexican,  Australian,  Hawaiian,  and 
Japanese  woods  generally  come  in  the  shape  of  roughly  hewn  timbers, 
the  sizes  ranging  from  14  by  14  inches  up  to  36  by  36  inches  and  from 
10  to  20  feet  long.  These  rough  timbers  are  sawed  into  veneer  stock, 
boards,  and  planks,  as  wanted. 

Eastern  oak  makes  up  by  far  the  largest  amount  of  hardwood  used 
in  California,  with  hickory  next,  followed  by  maple,  ash,  and  cotton- 
w'ood. 

Some  of  the  hardwoods  have  a  variety  of  uses,  while  others  are  con- 
fined to  special  lines.  Of  the  eastern  woods,  ash,  maple,  hickory, 
elm,  and  birch  are  used  chiefly  for  wagon  stock,  only  a  small  part 
being  used  as  lumber.  Oak  is  largely  used  for  cooperage,  lumber, 
and  wagon  stock,  in  the  order  named.  The  term  "lumber"  includes 
boards,  planks,  and  timbers.  Oak  lumber  is  imported  for  such  uses 
as  flooring,  inside  finish,  furniture,  cabinet  work,  bank,  store,  and 
office  fixtures,  paneling,  wainscoting,  picture  molding,  and  doors. 
The  black  walnut,  cherry,  and  tulip  poplar  from  the  East,  the  prima 
vera,  poplar,  and  mahogany  from  Mexico,  the  koa  from  Hawaii,  the 
red  bean  from  Australia,  and  the  Siberian  oak  from  Japan  also  go 
very. largely  into  special  lumber  orders  like  the  oak.  Basswood  is 
used  in  the  upper  parts  of  wagons  and  carriages  and  especially  for 
work  in  pyrography. 

A  California-grown  eucalypt,  the  blue  gum,  has  been  made  into 
insulator  pins  which  have  proved  very  satisfactory.  It  is  also  used 
quite  extensively  for  cordwood,  to  some  extent  for  piling,  and  is  being 
tried  in  the  form  of  veneer  for  furniture  and  interior  finish.  It  is  very 
probable  that  the  use  of  blue  gum  in  California  will  be  considerably 
enlarged  in  the  near  future.  The  black  cottonwood  is  used  princi- 


SUGGESTED  USES.  31 

pally  for  fruit  baskets,  and  for  this  purpose  is  cut  into  veneer  one- 
twentieth  of  an  inch  thick.     Some  is  made  also  into  wagon  stock. 

The  cost  of  all  hardwoods  is  high.  Ash  and  plain  oak  average  $100 
per  thousand  board  feet,  while  quartered  oak  and  hickory  average 
$125  per  thousand.  Iron  bark  brings  about  $105  per  thousand,  and 
Siberian  oak  about  $80  per  thousand.  This  includes  the  cost  of 
transportation. 

SUGGESTED   USES   FOB   TANBABK   OAK. 

Up  to  the  present  time  little  has  been  known  of  the  possibilities  of 
tanbark  oak.  The  feeling  has  been  that  the  wood  was  subject  to 
checking  and  warping  to  such  a  degree  as  to  render  its  use  impracti- 
cable. All  hardwoods  are  more  or  less  subject  to  these  defects,  and 
it  is  believed  that  the  difficulties  encountered  in  seasoning  tanbark 
will  prove  no  greater  than  those  which  have  been  overcome  in  some 
of  the  eastern  hardwoods.  In  fact,  the  experiments  made  by  the 
Forest  Service,  which  it  must  be  remembered  were  conducted  under 
unfavorable  conditions,  showed  that  the  wood  can  be  seasoned  in  a 
dry  kiln  in  such  a  manner  that  more  than  half  of  it  will  be  satisfactory 
material  and  only  10  per  cent  badly  checked. 

The  lumber  company  mentioned  as  manufacturing  tanbark  oak 
flooring  has  had  several  experimental  floors  laid  and  in  all  cases  they 
have  proved  satisfactory  under  hard  usage.  About  200,000  feet  of 
flooring  has  been  made  up,  and  about  1,000,000  feet  of  lumber  is  in 
process  of  drying.  In  sawing  this  lumber  the  regular  equipment  of  a 
redwood  mill  was  used.  Tanbark  oak  seems  well  suited  for  flooring. 
It  has  a  pleasing  grain  and  color  and  the  necessary  hardness.  By 
using  short  pieces  of  the  same  length,  say,  from  9  to  18  inches,  grooved 
and  tongued  on  the  ends,  as  well  as  on  the  sides,  the  material  can  be 
closely  utilized.  In  laying  a  floor  from  such  pieces  a  pleasing  effect  is 
obtained  by  having  each  strip  of  flooring  break  joints  with  the  strips 
on  each  side  and  by  alternating  the  light  and  dark  pieces  in  each  strip. 

It  is  quite  probable  that  tanbark  oak  will  prove  suitable  for  tight 
cooperage.  There  seems  to  be  a  feeling  at  present  that  a  contained 
liquid  would  be  affected  by  the  wood,  but  so  far  as  is  known  the  wood 
has  not  yet  been  given  a  fair  trial.  In  regard  to  the  tannin  in  the 
wood,  there  is  said  to  be  a  higher  percentage  in  the  case  of  eastern 
white  oak  (1.32  per  cent)  l  than  in  the  case  of  tanbark  oak  (0.63 
per  cent).  Of  course  there  may  be  other  constituents  that  render 
tanbark  oak  unfit  for  use  as  a  liquid  container,  but  it  is  at  least  worthy 
of  a  trial. 

As  an  inside  finish,  tanbark  oak  has  the  beautiful  figured  grain  of 
other  oaks,  and  there  is  apparently  no  reason  why  it  should  not  give 

i  See  Yearbook  for  1902,  U.  S.  Dept.  of  Agriculture,  article  entitled  "Chemical  Studies  of  Some  Forest 
Products  of  Economic  Importance." 


32  CALIFORNIA  TANBARK   OAK. 

satisfaction.  This  seems  to  be  proved  by  a  number  of  finished  speci- 
mens of  the  wood  now  in  the  Forest  Service  offices  in  San  Francisco. 

The  mechanical  properties  of  tanbark  oak  render  it  suitable  for 
wagon  and  car  stock.  In  bending  and  crushing  strength  it  compares 
favorably  with  eastern  oak  and  hickory,  which  have  for  so  long  been 
used  in  such  construction.  In  drying  it  shrinks  about  the  same 
amount  as  red  oak.  Tanbark-oak  bolsters  for  logging  trucks  are  in 
use  and  giving  satisfaction.  A  number  of  strips  of  tanbark  oak  1J 
inches  thick,  4  inches  wide,  and  6  feet  long  were  steamed  and  bent  at 
a  wagon  factory  in  Oakland,  Cal.,  with  as  good  results  as  with  white 
oak  under  similar  treatment. 

Under  present  methods  the  price  of  bark  f.  o.  b.  track  in  the  regions 
of  production  averages  $15  per  cord.  The  fuel  wood  from  the  trees 
that  furnished  this  cord  of  bark  would  amount  to  about  2  cords, 
worth  on  an  average  $5  per  cord  delivered  at  the  nearest  railroad. 
Bark  and  cord  wood  together,  then,  would  be  worth  $25.  The  2  cords 
of  fuel  would  amount  to  about  1,600  feet  board  measure.  If  half  of 
this  is  suitable  for  boards,  it  is  evident  that  with  the  present  price  of 
oak  lumber  the  returns  would  be  greater  if  the  tree  were  cut  into 
lumber  rather  than  cordwood. 

In  conclusion,  there  seems  to  be  no  good  reason  why  tanbark  oak 
should  not  take  its  place  in  the  Pacific  coast  hardwood  market  for 
many  if  not  all  the  purposes  for  which  eastern  hardwoods  are  now 
imported;  and  if  this  is  true  lumber  companies  owning  tanbark-oak 
stump  age  could  profitably  take  up  the  utilization  of  this  wood  as 
lumber.  In  California,  particularly,  where  such  large  quantities  of 
hardwood  are  imported  at  a  high  and  constantly  increasing  cost,  a 
native  oak  with  both  properties  and  appearance  that  compare  favor- 
ably with  eastern  oaks  ought  not  to  be  allowed  to  go  to  waste,  but 
should  at  least  be  given  a  commercial  trial. 


APPENDIX. 


DISTRIBUTION  OF  TANNIN   IN  TANBARK  OAK. 


By  C.  D.  MELL.        * 

Tannin  is  found  in  most  plants  and  almost  exclusively  in  the  living 
cells,  though  there  are  some  in  whose  cells  it  is  not  found,  such  as 
European  hackberry  (Celtis  australis  Linn.),  white  mulberry  (Morus 
alba  Linn.),  black  elder  (Sambucus  canadensis  Linn.),  honey  locust 
(Gleditsia  triacanthos  Linn.),  black  locust  (Robinia  pseudacacia 
Linn.),  and  laburnum  (Cytisus  laburnum  Linn.).  It  is  always  in 
the  form  of  a  solution  in  the  cells  and  not  in  the  cell  membrane,  nor 
in  its  primary  membrane.  Tannin,  chlorophyll,  and  starch  are 
closely  associated;  tannin  and  chlorophyll  together  in  collenchyma 
and  phelloderm,  and  tannin  and  starch  together  in  the  same  cells  in 
pith  rays.  Tannin  is  most  abundant  in  the  elements  outside  the 
cambium,  and  in  a  few  cases  it  is  present  sparingly  in  wood  fibers. 

An  investigation  of  the  tannin  contents  of  a  number  of  trees  shows 
that  several  of  the  elements  of  tanbark  oak  have  tannin  distributed 
through  them,  as  shown  in  Table  12.  Tannin  is  present  in  such  of 
the  structural  elements  of  each  wood  as  are  indicated  by  the  letter  x. 
The  small  circle  indicates  that  the  tannin  content  in  the  element,  so 
marked  is  very  small,  and  of  no  importance  in  connection  with 
commercial  operations. 

TABLE  12. — Elements  of  pith,  wood,  and  bark  of  trees  containing  tannin. 


Quercus  dcnsiflora  Hook,  and  Am.  (tan- 
bark  oak) 

Alnus  glutinosa  (L.)  Gaertn.  (black  alder). 

Betula  papyri/era  Marsh,  (paper  birch) 

Carpinus  caroliniana  Walt,  (blue  beech)... 

Corylus  americana  Walt,  (hazel) 

Satix  purpurea  Linn,  (purple  willow) 

Platanus  occidentalis  Linn,  (sycamore) 

Hamamelis  virginiana  Linn,  (witch  hazel). 
Acer  platanoides  Linn.  (Norway  maple)  ... 

Rhus  cotinuft  Linn,  (young  fustic) 

Pyrus  communis  Linn,  (pear) 

Eucalyptus  cordata  Labill .  (gum ) 

Ribes  rubrum  Linn,  (currant) 

Syringa  vulgaris  Linn,  (lilac) 

Fraxinu*  americana  Linn,  (white  ash) 


Structural  elements  containing  tannin. 


x° 


\° 


x° 


33 


34  CALIFORNIA   TANBARK   OAK. 

To  determine  correctly  the  distribution  of  tannin  in  plant  tissue, 
it  is  best  to  fix  the  tannin  content  in  such  a  manner  that  it  becomes 
hard,  compact,  and  easily  recognizable  under  the  microscope  in 
transverse  and  longitudinal  sections.  Tannin  hardens  into  a  compact 
mass  when  treated  with  potassium  bichromate  and,  in  transmitted 
light,  has  an  intense  red-brown  color. 

The  ultimate  twigs,  obtained  from  growing  trees,  are  cut  length- 
wise through  the  pith  and  are  allowed  to  dry  for  12  hours  in  a  room 
of  ordinary  temperature.  Then  they  are  soaked  in  a  solution  of 
potassium  bichromate  for  a  week  before  the  sections  are  cut.  The 
material  must  be  treated  before  it  is  sectioned,  otherwise  the  tannin 
content  will  be  distributed  by  the  knife  into  elements  where  it  does 
not  naturally  occur.  The  color  does  not  change  when  the  sections 
are  mounted  in  glycerin,  so  the  sections  may  be  preserved  in  this  way 
for  classroom  or  other  demonstration  work.  The  first  8  or  10  sec- 
tions should  be  discarded,  because  they  will  include  the  outer  cells 
coated  by  tannin  that  oozed  out  when  the  twigs  were  first  cut;  and 
they  are  likely  to  be  disappointing  because  they  will  not  show  the 
undisturbed  tannin  content.  The  cells  in  which  tannin  occurs  will 
be  filled  with  a  compact  red-brown  mass  (Pis.  IX  and  X) ;  or  there 
may  be  only  a  few  small  red-brown  globules,  as  in  the  pith  ray  cells 
of  European  alder  (Alnus  glutinosa,  L.  Medic.). 

An  investigation  of  this  sort  shows  that  tannin  is  present  in  the 
twigs  of  tanbark  oak  as  well  as  in  the  older  bark,  and  that  tanning 
extract  could  be  made  from  the  twigs  and  smaller  branches,  as  in 
the  case  of  the  eastern  chestnut  (Castanea  dentata).  Yet  there  is 
but  little  tannin  in  the  wood-parenchyma  elements  of  the  heartwood 
of  tanbark  oak,  so  that  tanning-extract  can  not  be  got  by  chipping 
the  wood  and  subjecting  it  to  tanning-extract  processes,  as  in  the  case 
of  the  chestnut. 

o 


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